There was a time when Steam updated about once a week, now it updated every time I open it, have I got my setting wrong?.
Steam will always run a check for updates. If you cancel it, Steam refuses to continue to load. It's been like that for a while, not sure how to prevent that.
I have run into a similar issue while playing in some cases it caused TS2020 to freeze up and stop running, I am not sure what else can be done to prevent it from updating at the worst times.
It's like Windows Update. "It is time for the updating of your PC. I will interrupt your stream that you just started to do so. You will then be required to reboot. You will answer 'Yes, Master'."
Actually with Windows you select your active hours in which you do not want to be disturbed and it has worked so far for me in that aspect.
Even so, in my case, I'm going to be installing something to block Windows Update sooner or later. I have read about another recent update that causes blue screen issues, and this happened to me in 2017 on Windows 7. I have to see if my audio stutter issue is fixed first.