Time of Season Affects Placements?

I just finished my placements for this season and went 7-3 and got bronze 1. It was a fresh account and had like 3 games of preseason ranked played or something like that. Last season (in like September) on a different account that was brand new and never played ranked before I went 7-3 and got Silver 1. That seems like a huge discrepancy granted that I went 7-3 on each account. I'm just curious if earlier in the season they are more strict with the initial placement than later. And if this is the case that doesn't really seem fair to me. Why would you even bother trying to complete your promos early on.

Additionally if you could offer other explanations for this please do.