Yes, that's right – The more XP you're required to get to level one of these 2 skills up, the less XP you gain from the gym.
At level 10 the XP goes down from 0.9->0.6
At level 25 the XP goes down from 0.6->0.3
This is such a stupid way to nerf the gym that it actually boggles my mind how anyone could've thought this was a good idea. At most you're getting 13.5 XP combined every 24 hours, which is barely more than the XP you would get from 1 raid
but it drops down to 4.5 XP COMBINED EVERY 24HOURS after you reach lvl 25 in both Endurance and Strength – 4.5XP is equivalent to running for 1 stamina bar.
This makes the already bad gym into a decoration, and the only reason to get it is to get rid of the even stupider debuffs that you get until you make it
