OG, I've competed with 3 females in standing heat, ready to be bred. All three of them won, showing the exact same as they had when they weren't in heat.

I've also looked at some during schooling, that were nowhere near the same dog as they were when not in heat. In those females that weren't the same, I could tell inside of 5 minutes what I wanted to see, so I simply put them up and stored that in my memory.