A big benefit of Android, its modular and bits and pieces can be updated independently. Part of the reason iPhones require to have long term OS support is the fact that their browser would otherwise be stuck at an old version.

You have it backwards. In the early days Android didn't have any components in the Play Store and Apple still provided updates for much much longer than Android manufacturers.

Google moved the web browser component to the Play Store because Android's OS updates are so bad. They had no choice but to do it.

Apple could do it too if they wanted to but they don't need to because they actually provide OS updates for a decent period.

Regardless of the history though, now, Chrome (+ webview) and Firefox on Android receive at least one update per month (sometimes more frequently). Thats a plus.