It matters for several reasons.
1) He's been lying about it ever since.
2) in the conrext of our conversation, it totally wipes out any relevance for your spurious sermon about " as if all Russian lawyers have access to Putin". The issue is what Trump thought he would get and what he could do with it, not whether every lawyer has info. You love to deride the GLW crowd for hypocricy yet write off any against your own side as minor or unimportant.
3) it calls into question whether anything the Trump camp claim about Russian involvement can be trusted and specifically kills Jnr's credibility.
4) related to 1, his foreknowlege and belief may prove to be the legal problem that experts in the US are talking about. But apparently you can pontificate on that but others cannot.
And its been a long time since i adherred to the "well they're doing it too" tactic of arguing, lol.