Still waiting on any sort of official communication on this issue, Square..

I'm also still waiting to hear back on some follow-up questions from Square's data controller but in the mean time the data regulator in my country has advised that the GDPR 'right to erasure' is not equivalent to 'right to rectification'.
That means as far as I understand, if you ask SE to amend details and they ask if you are asking for the erasure of your data/ deletion of your account, that is not an acceptable substitute for data rectification.

The more you know!