Dunno. To me it seems they never thought about the numbers on conduits beyond ilvl 200, rushed game development in a nutshell.
And why do I come to this conclusion? Well I’m bored to hell, so I’ve got nothing else to do but to scroll the bug report forum, and I found another person with a similar issue, just like me.
https://us.forums.blizzard.com/en/wow/t/discipline-of-the-grove-conduit-200-vs-213/835410
Oh, and very far down I also found this gem:
https://cdn.discordapp.com/attachments/785920576744718397/801527377560731698/unknown.png
Had a good laugh already.
Anyway, my advice to everyone is: don’t upgrade your precious conduits past ilvl 200. Especially potency conduits. You might just nerf yourself in the process.
Edit: reached the 5 days ago posts and also found my thread, where I posted the GM’s response.