No way, 800 is way too conservative, if you tell someone that they can take a lvl 1 fort with 250 cats, then they can take a lvl9 oasis with 500 cats easily.
The forts figures are way too conservative as well, I've been seeing the figures on this guide gets thrown around alot and frankly I don't think the person who made it ever farmed a fort above level 6, or if they did they didn't try to find what is actually an optimal amount of cats to take everything out.
18k for level 10 fort? way too high, 14k is plenty and that is being extra safe, with high attack stats and tech and equipment, 10k is enough for most people for level 10 forts.
Same principle goes for level 9, 8, 7 and 6, figures listed are way too conservative, the vast majority of people can farm them with alot less cats. Basically the figures listed are for people who barely upgrade their stats, don't upgrade their techs and don't bother getting any equipment; but if you don't upgrade your setup then why even bother farming level 10 forts.