I don’t understand how they are supposed to “sell your data” if you just never use a Mozilla account and uncheck all the telemetry. Its not like they can secretly steal your data, since its Open Source.
It seems to me like just more FUD that Google is spreading to undermine our trust in free software.
The current intention may not be malicious, but it leaves the way open for changes that are to slip in. If they were worried about services like translation being concidered ‘sales’, which is a reasonable concern, they should have split them out of the core browser into an extension and put the ‘might sell your data’ licence on that.