Is the solo/duo and flex queue bugged?

Greetings, I was wondering the logic behind the solo and flex queues, I'm currently Gold on flex and Diamond on solo, yet it won't let me invite my friends to flex unless they are bronze or unranked, or plat 3-diamond 2.

I find extremely weird... I understand the logic in solo queue, and it won't let me invite anyone who isn't between plat 3 - dia 2 indeed like it should be, but on flex it gets extremely weird, my friends can ONLY invite me through suggested players although we're both gold in flex, I can invite bronze or unranked players to my flex and viceversa, or plat 3 - diamond 2, although i'm only gold in flex, and this goes along with my friends as well it's not that my client alone is bugged or something.

So TLDR, the criteria to invite players into my flex queue is mixed with the ones from solo queue, is this only me? my account? everyone?