I think it's a matter of training the gmail filter. If you don't properly mark spam and unmark false positives, it doesn't have any feedback from you.

I noticed that if I accidentally mark certain emails as spam, then such emails end up straight to spam in the future.

Maybe, but email about UK Lottery won't make it to your inbox at all, or so was my experience anyway. Gmail team probably had to train the model during that long period of beta (three years if I remember correctly) so it makes sense to account for user feedback. I would be surprised if they still do it now.