Why couldn't it be? Thats just as possible as any limit on power. Think that after a certain point they thought Battleminds had too many power points, and decided to lower the number they got. Think that you saw the power descrepancy showed up usually around level 13-15. Whered o you lower the number of power points they get.
The progression works in such a way that a psionic character can't spam their highest level at-will attack power at its highest augment more than twice per encounter at the paragon and epic tiers (and even then, at the lower ends of the paragon tier, you'd have to dip into the 2 power points granted by your paragon path which is supposed to augment your 11th level encounter power). The only time you can spam your highest level at-will power at its highest augment more than twice per encounter is between 7th and 12th level, when you can spam your heroic tier augment 2 powers 3/encounter if you wanted (actually four times between 11 and 12th levels if you forgo augmenting your paragon path encounter power, assuming you have one).
Basically, the progression encourages you to spread out your power points instead of spamming the highest level powers and exhausting yourself quickly. Also, the restriction prevents you from using the highest augments of your highest level at-will power repeatedly, which would be "unfair" to characters with a normal power progression in terms of power equivalency (the psionic character can already use its "highest level encounter power" twice per encounter if it wants, so third time would be pushing it). Its also the reason why the progression temporarily shifts between 7th and 12th level. At 7th level, you'd normally have 3 encounter attack powers (1st, 3rd, and 7th); a psionic character could theoretically use its 2-point augment from its remaining 1st, 3rd, and 7th level at-will powers, which should be equivalent to the normal progression (BTW, the progression only works at higher levels if the 1 and 2 point augments of the higher level powers are the equivalent of a lower level encounter power). Of course, to get the power and power point progression to work out correctly, the psionic character gets a (potentially) slight edge at the high heroic and low paragon tiers since it can spam the 2-point augment from the 7th level power 3 times instead of using its lower level powers, though at the cost of versatility.
It also explains why the epic tier at-will powers do not scale automatically to 2[W] when they are unaugmented (at least for the battlemind, the ardent is a bit funky because it has close powers at those levels which keeps the damage dice smaller). Beginning at 21st level (assuming you trade in your at-will powers like the progression intends), you will always have a 2-augment power that does 2[W] damage (between levels 21-22, its your level 7 power, at levels 23-26, its your level 23 power, and between levels 27-30, its both your level 23 and 27 power).
You definitely become disadvantaged if you go nova and exhaust your power points immediately with your highest augments, but how many times in an average fight (which lasts what, 5-7 rounds) do you use all of your encounter powers? Mostly, its a mixture of at-will and encounter powers. So at 21st level for example, you could unleash a 4-point augment of your 17th level power, a 2 point augment of your 11th level paragon path power (why not, its "free"), and two augment 1 powers from your 17th and 13th level power (probably roughly equivalent of a 7th level encounter power). If you had 11 power points (and 2 from the PP), that would leave you enough room for two 2-augment 7th level powers (epic at-will damage) and another 1 point augment from 17th or 13th level power. At 23rd level, you could unleash a 6-point augment of our 23rd level power, a 2 point augment of your 11th level paragon path power, and two augment 1 power from your 17th and 13th level powers, leaving you enough room for two 2-augment 23rd level powers (epic level damage) and another augment 1 power from your 17th or 13th level power. Unfortunately, accuracy becomes a premium for psionic characters when it comes to attempts to hit with the 2-point powers, so if it looks like your going to suffer significant penalties on an attack, use an unaugmented or 1 point power instead.
Of course, you can perform all kinds of power combinations with your power points and there other powers that you could augment, like magic item powers and the battlemind's marking class feature. It also becomes more interesting if there are more ways to gain power points during an encounter; there are at least three ways now, the psion's exchange power feat, the cerulean adept
seal the threshold attack power, and the steel ego PP feature psionic cascade. Also, it stands to reason that there are psionic epic destinies that may also grant power points.