Ah. I turned off all the general settings toggles (manual fail, skip checks and futa+. Which I believe were all on by default?) and speedran perfect toy again and now I see the +.
Edit: I turned them back on one by one and now I'm able to get the ironmode 'chieves with the same settings as before. I'm guessing there was just a bug somewhere that's been resolved. No idea how to replicate whatever that was.
Thanks for the response anyway. Prompted me to fiddle with the settings