Why if adding Team Builder on PBE should Also Coincide with other game types

I understand that most people go on PBE initially to test out new champs, champ skins, textures etc. However, I don't fully agree with the idea that while doing so we can not have only one game mode or type rather. All of the testers shouldn't have to wait an entire 3-5 days in order to see a change on the client game modes. Rather all testers should be able to have different game modes including Team Builder(if necessary).
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