I don't think anyone's tearing down people who are upset. Anyway, I don't mean to, and if anyone is tearing, that's mean and uncivil and not very nice.
That out of the way...
They're putting more monsters into this MM than we had in the last one. I'm willing to bet that that's counting Orc Scout as a separate monster from Orc Soldier or whatever, but the point still stands that there's a pagecount limit, and stat blocks chew up space, and (using MM V and so on as an example) the book will be more usable as is, due to statblock layout.
They've pointed out what they're doing with this book, which is asking each monster through the gate what its unique schtick is. If one can't be found, it goes back for a later book.
I suspect that the only exceptions to this rule are the animals, and they're such a small portion of the book, it's incomparable.
So the question is, given page count and editorial constraints, which would be better:
-] An extraordinarily abbreviated frost giant stat block.
-] It goes in, and a monster with a good, unique ability goes out (extend them the level of trust of not ranting that they're giving us another yrthak; assume the designers are capable of learning from their mistakes. That's an order

)
-] It gets changed, so that its abilities are unique. Note that this is a fairly massive change: ogres and hill giants have more traction, so it's only fair that they inherit the whole giant panoply. I think people would complain a *lot* if frost giants could suddenly toss Otilukes' or were summoning monsters or whatever. That's been my experience with every other change, anyway.
The frost giant getting pushed off a book or two (appearing as an iconic in the frostburn equivalent, say), is the least of three evils, to me.
Everyone's mileage will vary, I'm certain.
What would make me happiest is option 1 -- in the form of a list of instructions on how to palette-swap a fire giant into a frost giant.
What will in fact happen is that the frost giant will appear either in MM2 or in the Frost Burn analogue.
Which, really... if you used guardinals heavily, this was a price you paid in 3rd edition; if you used archons, your choirs were scattered all over the map.