I suspect that their thinking is along the lines of approach. That is, the DM determines not only how fast HP recharge, but when you actually get that opportunity (through not-so-wandering monster attacks and the like.) It may not be great thinking, but I wouldn't be surprised by it.
That can work - I use a version of it in my 4e game, for instance - but it helps to be explicit about it, so GMs know what they have to do to make the game work!
The good thing about 4e in this respect, though, is that it's not on any sort of knife-edge - the PCs are resilient enough that it's hard to kill them by pushing too hard, and the intraparty balance (due to roughly symmetrical resource payloads) is such that if I'm too relaxed no one is systematically disadvantaged (though the player who horded dailies on that particular occasion might feel a bit ripped off).
The other thing is that 4e lacks, at least as routine elements of play (some rituals push this envelope a little bit), the teleport/rope trick sort of stuff that makes it hard for the GM to exercise this sort of authority consistently with the rules of the game. So far, D&Dnext doesn't seem to be adopting such a strict approach.
The tension created between continue or rest I find enjoyable in games. Do we rest because the Wiz is out of spells? Do we rest because the Cleric can't heal anymore today and the fighter is down HP? Do we rest because half the party is out of resources? These conflicts add to the dynamics of the game and make the game interesting for me. If everyone is on the same schedule it becomes boring. I want discussion and planning at the table. I want resource management to matter and I want it to matter to players in different ways reflected by classes and how players play those classes.
Two things.
First, having every PC on the same recharge scheule with the same resource load out doesn't eleminate the need for resource management or operational decision-making. I've GMed all-thief parties in AD&D. They use their abilties on the same cycle (at-will) and regain their hit points on the same cycle (per day). And there can be disagreements and decisions to be made (eg PC A is at full health, PC B has lost 5 hit points: do we rest or do we go on?). I have GMed all-caster parties in Rolemaster. They are all on a daily cycle for spell point recovery, but it can come about that one has used all his/her points when another has points left. And in my 4e game, PCs routinely have differing numbers of surges, daily powers etc remaining.
My reason for preferring a common recharge cycle isn't that it produces uniformity and a lack of operational decision-making - as I've just illustrated, it doesn't. It's that I, as the GM, am not introducing systematic advantage for one player or another by departing from a systemically-presupposed "adventuring day".
Second, what is the source of tension between resting or going on? In a system that relies on GM force, I don't see it. If you rest, the GM can decide to keep up the pressure by having "wandering" mosters disturb you. If you go on, the GM can decide to release the pressure by having all the monsters be sleepign when you go past them.
I think it's worth noting that Gyagxian D&D
doesn't leave this up to GM force - there are regular wandering monster rolls, reaction rolls, rolls to see if a dragon is aslep, etc. Gygaxian D&D, as spelled out in the AD&D DMG, also makes ingame time a resource via the rule that one real world day equals one ingame day - I can't say I completely follow the way Gygax was running his game, but it seems that if you sent your PC on a long trip or spent a long time healing, you might be at a disadvantage relative to other players in the same gameworld, who would form a party and loot all the best dungeons in the meantime.
Games like Runequest and Burning Wheel make time into a resource in a different way, by allowing you to spend it training (thus improving skills), or earning money.
As I said, I don't particularly care what approach the designers take, but I would like them to be deliberate, clear, and to spell out how they intend their game to work, and what responsibilities (if any) the GM has to make it work properly.