I'm fine with this.
MHA and Hori, while not exactly showering us with speed feats have been somewhat consistent with their information. When someone moves fast, it often takes a visual toll on them, such as Deku and Shigaraki's faces being pushed back by the wind...
This concept was also introduced in Vigilante.
Hori probably considers a character like Edgeshot incredibly fast in short bursts as he can circumvent this obstacle with his quirk (Mirio could too, technically).
Reaching and surpassing transonic speeds is actually wild, and it's not shocking this is Horikoshi's idea of their speed. It seems like he has a pretty large emphasis on immediate acceleration, and then the air working against them, which is pretty realistic. Such as Bakugo clearly breaking the sound barrier while using his cluster move, but aside from that burst, he's likely slower than Iida wholistically, who can maintain higher speeds for longer periods.
For those interested,
Thanatoseraph did a breakdown over at SpaceBattles