I get the feeling Valve felt the need to change this because the "communication abuse" report was kind of pointless. People just muted, or would fully report if actually pushed, and for some reason it was your only option for the other team. I don't know anyone who gets mad enough to report someone, but measured enough to specify communication report.
I don't think people are suddenly going to start getting communication bans because of people muting being their preferred style of playing, and we shouldn't assume that is the case until it actually starts happening. Any halfway decent report system is going to be looking for statistical outliers, and anyone using muting for their own playstyle preference is going to come out in the distribution.
People are always frustrated about toxicity in this game. To me this seems they are going to get much more data on who is actually problematic in chat and voice, just based on muting statistics. If it actually works, it would also hopefully less dilute the regular reports which might get better results on removing actual griefers, instead of them getting wasted on flamers.
Maybe you could argue they just shouldn't have added the word "report" to the name of the button, and just collected the stats silently. But at least they are being up front about how they are doing it.
Source: https://www.reddit.com/r/DotA2/comments/tnovr1/mute_report_is_a_better_system_no_one_used/