No worries mate, welcome to the forum btw too.
If continual 4 cylinder is known to cause other issues, then i'd just stick with letting it do what it wants to do. I haven't got any first hand experience of these models, I just knew the answer because i'm an engine nerd lol. Maybe just boot the throttle here and there if you've been in 2 cylinder mode for an extended period of time, just so you're not putting loads of unburnt oil into your cat at once. If it's enough oil that you can see it, then IMO it will definitely shorten the life span of your cat in the long term.
Edit: If you're new to the car then definietly keep a good check on the oil level. Eco engines and engines with cylinder deactivation often use more oil than more traditional designs. That's the main reason i said i don't think they are much benefit in the real world, as the slighty higher MPG is often offset by the fact they burn more oil.