I heard they set back levels to people who botted and apparently a lot of accounts during the last 5-10 years were hacked and used by foreign bots to farm osrs gold and sell it. When they released the email link thing, a lot of people restarted playing and got their account back without even realizing and there’s a possibility that they set you back for that reason but then you’d be able to see it on your profile. (It would say that at some point you got a ban for macroing.)
Do you really think this is the case though? You think someone who didn't bot and remembers his levels would log in years later to see his levels lower than when he quit because someone else botted on his account? He remembers his levels before said botting and they are lower. Not only that, but if his levels were lowered, he's have been banned and there would be record of that.
More likely than not, he just misremembers his levels or is getting them confused with rs3.