None of that makes sense (who told you that the replacement happened in the beginning of the BB cultural phenomenon, not centuries later when it had already spread to other cultures and peoples? A people is not defined solely by a certain type of pottery). Particularly your numbers are really off. What makes you think that to have a 100% replacement you need to have the same number of incoming males that the previous male population had? 100,000 men can impregnate 500,000 women just as much as 500,000 men. It's not like, quantitatively, males are as necessary as females to guarantee the reproduction of society. Also, we don't know if the post-replacement population was as large as the pre-replacement one.
Sorry, but I can't deal more with cult members and alike, I have the conclusion that you are not capable to have own thinkings, I can't discuss under such conditions:
- hocus-pocus, from underpopulated steppe, R1b-Z2103 conquers Central Europe, but changing it's Y-DNA to R1a, fine
- hocus-pocus, an Iberian culture (BB) is taken in Central Europe without autosomal effect, fine... but it expands back as R1b-L51 instead of R1a, and losing all previous cultural steppe traits by the way, fine.
- hocus-pocus, a 40% steppe or eastern component in Iberia needs to kill all male population (500000? 1000000?) to be replaced by 500000 or 100000 R1b machos coming without women (long trek...), fine.
- hocus-pocus, BA admixture graphs don't display any steppe component, it was lost by continuous dilution, fine.
as you and people alike can swallow all it, I only have the alternative to scare you, maybe you can wake up:
1. go to
https://www.biorxiv.org/content/early/2017/05/09/135962.full.pdf
2. go to extended data figure 1, admixture graph b (K=8)
3. look at Yamnaya, CWC, and Central Europe BB, check their CHG share, everything is all right?
4. look now at the Iberian side of the Beaker Complex (also a French BB), can't find that CHG?
5. ask then to yourself:
a) this only can be explained as Iberian BB were not coming from Central Europe?
b) this only can be explained as Central Europe R1b machos had a very hard gooooood time with Iberian brunettes that extracted their CHG?
com'on start to think by yourselves.