@imalwayshappy - I recently went through a total reseeding of a front lawn ( well seems "lawn" isn't quite the correct term to use now, maybe garden)... Anyway, I purchased lawn seed (not grass seed) no. 2 mix online and I'm seeing similar to you at these initial stages, but also a mix of "non grass" also - i.e. weeds.
The seed itself that I purchased, seems consistent, so I'm assuming that the "extras" I got growing were part of the top soil / manure / moss peart / sand mix, that I added to enrich the soil before seeding and a helping hand from nature itself, in general spreading it's seed. Did you add top soil / moss peat / etc to the soil that could account for the Poa Annua ? Are you seeing anything besides the grass / Poa Annua in the garden?
I'm hoping that the grass itself will increase in strength & take over the areas that I'm currently handweeding... It's a relavitely small area, but still consumes a lot of time trying to clear things out..