That still doesn't put the "expectation" or deadline on us, the consumer. Which was part of your original point.
Okay, try to wrap your mind around this concept.
Developers are hard pressed by something called a deadline, set by the people who they owe tons of money to.
This affects the consumer because whether you like it or not, you are one of the people who give the money back that was given to the developers, and something called profit that's the original reason the people who gave the money, gave the money. Let's call them investors.
The deadline affects you because they need you to pay the money by the time the investors expect it, so the expectation is, by proxy, also on you.
If the devs give you a game where you can play custom variations or without custom variations and you choose which, more of you are likely to buy the game than if only one or the other is true about the game.
Currently, there is going to be a mode in which you can use custom variations and fight people who use them, and one where you cannot.
They would STILL have such different modes even if they decided to allow custom variations in tournament play, because options are good.