> It does significantly lower the bars for identifying you though, but the requirements are still high
If you squint a bit, it looks a lot like a "Nobody But US" (NOBUS[1]) scheme. A few more identifying bits could tip the scale for party that has a whole host of other bits on a list of suspects, without being useful to most other people.
You definitely need glasses then.
Let me specify: The user must have entered his data on one site which the attacker has control of. That is a high bar still.
Then why complicate it by being publicly insecure? If Mullvad were wanting to defeat anonymity, they could simply log the traffic metadata while falsely advertising they aren't.
Their ads on San Francisco's public transit are good.