I'm Pretty Confused As to How the Unranked Climb Works

So this is my first time since Season 3 starting Unranked. I decided to make a smurf account so I could have a second account to climb on where I don't have to be as stressed or try as hard, and also to have a better understanding of my skill level (if I can get to my same rank twice then I deserve that rank).

So I place in P1 on my main, skip from D5 to D3 gaining +27 per win.

I place in S5 on this account. Skip from S5 to S3. I'm gaining +27 LP each win. But for some reason I didn't skip from S3 to S1, even though I'm still gaining the same amount of LP. I know for a fact that LP gain has to do with MMR, and by that logic (the fact that LP gains are the same) if I skipped a division before I should skip a division again. Why didn't I skip from S3 to S1?