I was under the impression this is a YMMV trope, so there is no objective truth to be sought.
Even if we consider it objective, I read several comic book material about the character and he manifested no attraction to guys before, the reason why it was quite a shock to read that issue. Chuck Dixon wrote over 100 issues of Tim Draken's Robin series and he personally said he never wrote him as bi in any whatsoever. And I'm pretty sure he is the guy who wrote most issues where Tim Drake is the main character than anybody else on the world, so it's good as Chris Claremont word on the X-Men, even if he isn't the main creator.