Grass seed question

Not to be nit picky but since you asked, no it won’t stop germination but it won’t allow the plant to grow past the germination stage. It’s easier to say it won’t allow germination, which is why I think you hear that so often.

I would wait until July/August if you want to try seeding this year. That would give you 2 solid months for the new grass to take before entering dormancy.