Not at all! I believe everyone should ask as many questions as they need to understand the rules. There have been debates on this forum about lesser issues and I have been at the forefront of many of them
Consider if it were an issue of language and interpretation: what if the Shadow Player had and used 3 Orc Assassins and the Fellowship only had Frodo and Merry? Would the Fellowship be totally unable to assign the 3rd Assassin because none of the Hobbits are defender +1, letting the Shadow player put that minion wherever? Or would the Free Peoples player be allowed to assign more than one minion to a companion with no defender bonus? That's what your understanding would have to allow for. And what about other cards that make a player do something (discard a card, exert a minion, etc.), are players allowed to do that later in the phase as long as it's the same phase?
Luckily for everyone, the rules don't leave this up to semantics:
Each phase action must be completely performed before another phase action can be performed.
The wording of
Orc Assassin prevents your interpretation. If a player is made to do something as a result of a phase action, they've got to do it right then and there. If the Free Peoples waits until assigning defenders to assign the
Orc Assassin, how can that action have been completely performed?
Orc Assassin does not reference another point in time for the action to take place, such as "Spot 2 Hobbit companions to make the Free Peoples player assign a Hobbit to skirmish this minion
when assigning defenders," so it is not an action creating a future restriction. It must resolve once activated. I think this wording is what you're saying, but what would happen if the Free Peoples player ran out of Hobbits? The Shadow Player gets to assign the minions, or free Defender bonus for Hobbits?
There are other ways to word the card to get the effect you want, but in any case 4x of this minion against a Fellowship with 2 Hobbits would probably mean that 3 of them end up on Frodo without much opportunity to do anything about it. Plus
Bill Ferny, Swarthy Sneering Fellow and you have a nice bomb to try to lay on your opponent
Tol Brandir would be brutal and extra Hobbits would be a huge liability.