How would an optional, official parser be toxic?

[SleepyNeko]

And the players using it to be toxic can be reported and reprimanded just like they can now. As far as being exclusionary due to more availability...as it stands now there's 100% availability on all the logs people care about. So what would be the actual change here?

Well the "silently" excluding people cannot be reported. You can argue that people are doing it already but it is still true that having an official parser will "promote" more people to use it leading this scenario to occur more often.

It is same as the WoW Addon, even though they don't support it, they also don't restrict it, therefore it is more accepted to drop "under performing" players and benching others.