Hello,
The reason why is up for dispute, but the ruling is this way as there was originally only 7 differently named Crystal Beasts.
Konami did not future proof this archetype in the case they printed different crystal beast names.
Unfortunately this means that having MORE than 7 results in you not being able to summon the monster. As such, this is how it is ruled in Omega.
In the TCG, because it is up to interpretation, we have sided with the OCG prescience, until there is an official statement from the TCG Konami team. In an actual TCG event, you should ask your head judge on how they will rule it before your event to understand how how it will work for that event. Because we have to apply a blanket ruling, we don’t have the luxury of going back and forth, hence relying on the OCG.
If you have any other questions, please feel free to ask the Judges in our #rulings Channel in the Duelist Unite Discord channel.
Thank you for helping to make Omega be the best it can be.