on one of my accounts i failed plat 4 promos 6 times (season 7) and still skipped plat 4 when i finally did beat them, i had a 85% wr and it was 65% when i beat them. you can lose them multiple times but it really doesnt matter.
in my case every single time i went 1/2 6 times thats 6/12 overall + 1 win to get back into them which is another + 6 then finally when i did beat them it was a +1 to get into them and clean 2/0 so overall 15 wins 12 losses
what did it matter if i beat them or not? my winrate wouldnt have changed overall it still would have declined if i didnt get the 12 losses in promos i would have got them at some other time in my climb. there isnt some losing curse for promos, and if you didnt have promos there wouldnt be any protection after ranking up.
its a common misconception that climbing is a direct correlation to rank its the furthest thing from the truth, its the mmr that matters
if you have good mmr you will climb extremely fast, usually skip divisions sometimes completely forego promos in general.