Questionable under what? And what constitutes a questionable age gap? Who decides? Your own private judgment. I’m 10 years older than my partner, my best friend is 22 years younger than hers. On what grounds other than subjective moral judgment can you decide? Does it matter if I’m 58 and my partner is 48? Does it matter if I’m 28 and they’re 18? We stick to the legal binaries and the law because everything else is just subjective opinion and judgmental bias masquerading as benevolent moral authority.