No. I do not believe they check anything after the account has been opened.
Yes they do now. Keep up.
We have known this was going to happen, about 4 years ago.
It was part of the Immigration Bill 2014 as it wound its way throught Parliament and the Lords and became the Immigration Act (law) 2016 in June 2016. The bank account checking part of that 2016 law, started in January 2018.
It's been so easy for illegals/overstayers/visitors to abuse the UK, i.e work, steal from the NHS, rent, delay deportation for years by keep appealing every visa they put in for that they won't get, etc, that the UK decided to stop everything that made it easy for these to abuse the UK. Hence all the rule changes and the two new immigration acts.