General Rule change saw from the Nids faq's Effects all armys

Q: If a unit has Advanced in a phase, and is given the
opportunity to move again in the same phase, what is their
Move characteristic?
A: Their Move characteristic for the second move would
still be the value as modified from the Advance.
For example, if a unit with a Move characteristic of 5"
Advances in a Movement phase, and the result of the
dice rolled for the Advance is 4, its Move characteristic
would be modified for that phase to 9". As such, if it was
given the opportunity to move again in that phase, its
Move characteristic would still be 9".

Kudos for spotting that.

That's interesting

Oh...a friend mentioned to me that advancing counts as a modifier to your movement value. I never put 2 and 2 together like that.

It makes sense to me, not really gamebreaking either way though.

Yeah not game breaking, but a rule that i havent been doing (it didnt/doesnt change much really).

If you played a ynnari solitaire you were probably already thinking of it this way

Sorry to necro, but there is something puzzling here.

Quicken, Twilight Pathways, and Warptime all happen during the psychic phase. They say the unit gets to move as if it were the movement phase, but you aren't still in the movement phase. So RAW, you still roll for the advance value the second time you move due to psychic powers. This is backed up by the core rules, which state that advancing increases the move characteristic for that movement phase, not for the entire turn.

How to Tyranids do the double move thing? Stratagem or psychic power?

Stratagem. Well both really.