nope, i tried it many times in different variations, e. g. sending dragon to g.y. with jesses skill or it was still in deck, but it never worked for me. i‘d agree, it‘s a bug.
I don't know what's wrong with the "still in deck" one, but sending the dragon to the graveyard with Jesse's skill never gonna work in the first place since Rainbow Dragon is never summoned properly, meaning Rainbow Gravity can't revive it.
Which is something that has been mentioned MULTIPLE TIMES in this comment section.
If you use the family skill with Jesse your deck needs to be clean of crystal monsters. The rainbow dragon from the skill CAN ONLY BE SPECIAL SUMMONED with the 7 other crystal cards from the skill. I used RG with crystal deck with the skill and the RG card worked but i could not activate the cards own effect of special summoning it because the 7 different crystal cards were my own and the skills
...That is straight-up wrong. (And yes, I just wasted two minutes of my time testing this in the off chance it did happen to be bugged or something. I had a combination of my own and skill-added Crystal Beasts, worked fine.) All your Rainbow Dragons were probably in the Graveyard without having been properly Summoned first.
Another possibility: the Rainbow Dragon is in your hand and you didn't notice this card only SS from Deck or Graveyard, hence why it doesn't work for you.