The reason for these checks will have︁ nothing to do with whether your relationship is 'good' or 'bad' nor whether you are︂ 'welcome' or not.
From my experience (UK) banks including HSBC will do intermittent AML checks︃ on account holders to check if the details they hold are still accurate/valid. And in︄ further checks if the purpose/reason for the account usage are still valid.
Typically, these checks︅ will be headed by a 'REFRESH' team that is conducting these checks. I have such︆ a letter from another UK bank.
If you don't provide the information they request, your︇ account will be suspended. You won't be able to put more funds in or out︈ until their compliance standards are met.
The bigger question I have for you is, why︉ not recognise and see this for what it is, 'standard' regular AML checks (every 6-12︊ months), which have only unfortunately got more stringent over the years?