OK so we know how he failed with Bugsy, but can he tell the gender of this (and that it's Ash's)?

 

 

Probably.  The guy most likely spends more time with Pokemon than human beings.  It'd explain why he'd need to ask them point blank if they were a boy or a girl, or forgetting the name of his own grandson.

He's using the fanbase instead of a wikia

I thought the Professor knew about Pikachu's gender since the day he gave it to Ash.

...you spelled decipher wrong

 

PROF OAK NEVER FAILS AT POKEMON I TELL YOU

Yet he fails at remembering his own grandson's name...

lololol I see the taaaape....

8D