Safari is a complete nightmare on this. Leave it for a few seconds, reload. Switch between tabs on my iPad Pro 2018 for too long, reload and any webform text is gone. It was fine on 13.1.3, I don’t expect perfection and know things will refresh after an extended period or if I’ve been flicking between loads of apps / tabs, but this is absurd.
It shouldn’t be happening on an iPhone 11 and iPad Pro. I didn’t bother with the betas because of people reporting this issue, but there it is in the full release! Apple either need to get a handle this sort of thing before updates are released to consumers or, if they can’t be bothered, pack the devices with a minimum of 16GB RAM to mitigate against it.