Kind of, but also because you'll require less support instructions for some of the features you can't use.
I'm guessing that strict would use some assembly code routines that are more efficient and shorter than non-strict because you have less surprises to expect.
It's like with some other compilers you have the option to for example drop array bounds checking, which can speed things up a little if your code is well behaved.
You're right though, it'd be unlikely to make that much of a performance difference but it may become more important as the compiler matures.
I'm guessing that strict would use some assembly code routines that are more efficient and shorter than non-strict because you have less surprises to expect.
It's like with some other compilers you have the option to for example drop array bounds checking, which can speed things up a little if your code is well behaved.
You're right though, it'd be unlikely to make that much of a performance difference but it may become more important as the compiler matures.