Yep. Definitely quite the interesting theory but I think it's just RNG being very very nice. I'd think crystal legends are harder than Eternals since not every legend can be crystal even at same % chance but it's interesting that you seem to have more crystal legends than Eternals found.
Although Eternals are just as rare, sometimes a little rarer but anything can be eternal. Well crystal legends are very nice for saving crystals though for sure .