Yes, but you also said that PBA had a good point. That’s conjecture unless we find a source to compare the two issues, one from YD and one from OC.
I actually think (as you said) it’s mashma in MB and Shaar Hatzion that any b’ein would be a problem in the nine days, even if it wouldn’t necessitate waiting six hours (although it might, depending on how you learn the Shach).