I'm sure everyone knows at this point since Bosstiary now tells us that Professor Maxxen is a Bane boss so repeatly killing this boss must be possible to complete the bosstiary.
I have killed him 7 times. After the first kill, I reported the quest and came back to farm the mount items.
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Proof:
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Please do let me know if any further evidence is required and I'll be happy to share or test further.