I must admit I have trouble seeing her endgame. As others have pointed out, the PM has sufficient seats to ensure that the eventual deal will go through unless it is so blindingly obviously bad that there is a sizeable backbench rebellion. Of course that may yet come, but in that case all bets would be off anyway.
On the other hand if the objective is to neutralise the SNP and Indyref2, then it would probably been wiser to hang on until after the local government elections at the start of May inasmuch as they would have been a litmus test for Nationalist support mid-term. For what it's worth i don't see any real change in the Scottish political landscape and even if a couple of seats went one way or t'other it would be difficult to see the SNP having anything other than a majority of (Scottish) MPs being returned.
All very peculiar indeed.
It may just be a delaying tactic on Scotref. It can probably quite legitimately now be parked for 3 months as a question.
Any reduction in SNP representation (and lets face it the only way they can go is down from their current position) can be spun to strengthen their position that Scottish people don't agree with the SNP on this one.
In that regard its maybe tactically fairly clever. It'll be interesting to see if the SNP have prepared for such a possibility and what their reaction may be.
I guess the base model response is fight it like a normal GE on a Scotref ticket and use a majority of MPs being returned as a clear mandate although I don't see how that gains them anything from today.
A high risk move might well be to use the GE as Indyref and run on a ticket of negotiating independence with Westminster. This used to be their position but they have since backed away towards the referendum approach.
I'm not sure what legitimacy that move would have with a few dozen Westminster MPs.
Could they double whammy it and have a Scottish Election on the same day in the hope of getting a clear SNP majority in Holyrood and using that as a mandate to declare independence? I don't think that would work either.
So, since the Tories have nothing to lose in Scotland and the SNP little to gain it might well be that May thinks there is not much at risk from her point of view. She can probably only end up in a stronger position.
The short timeframe on this probably also causes problems for any large scale tactical voting or political coalitions to form but I guess it could be a possibility. A Bremain Alliance forming might be interesting.