The Terminology MaxSpeed is used in order to describe the maximum speed that specific pokemon with the specific hidden power can get.
H.P. fire Serperior's maximum speed is AND can ONLY be 30 on his IV (individual value). so the title is correct you need to change your mindset on this point just.
You just think that max 31speed on IV is applied to every single pokemon, which is clearly NOT. but thats it from me. this is a auction topic if you want to know more you can DM me.
Peace