This is completely false.
The amount of experience required to gain a point of skill level is:
- k & C = are constants depending on the skill
- x is the current skill level
The values for sneak are:
k = 2/45
c = 32/3
Here are the experience required for the first 10 levels of sneak:
You'll notice that there is not much difference in the experience required early on as this is not a linear curve. To go from level 49-50 will require nearly 100 experience. This may lead to the false impression that staying at lower levels means your skills go up faster, but whats really happening is if your skill level is low, its easier to improve it.
As for whether or not you can gain every perk, the amount of experience required per level is:
Current level * 25 + 75
You gain the amount of experience points equal to the level of the skill you just obtained. The game will 'bank' any extra experience towards the next level, but the maximum experience you can gain in the game is absolute. There is no way to gain all the perks as you'll top out at level 81 even if you choose to not level up at all until you max all your skills.
Here is the entire XP curve for Sneak in case you are interested: