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.