I don't use old Reddit, and haven't noticed this behaviour either.

Sounds like maybe some prevention against this is already implemented in either particular Android browsers, or ad blockers, maybe even for specific sites?

Just speculating, I can't imagine a reason why they'd implement this especially for Safari.

Other than A/B-testing or trash code that coincidentally doesn't work in all mobile browsers.

Maybe they use the same AI that generates their fictious relationship stories to add these dark patterns to their code base :D