On the dndbeyond character sheet, on speed, if you select "speed"
You get a lot of boiler plate text, which includes
"Every character has a speed, which is the distance in feet that the character can walk in 1 round. This number assumes short bursts of energetic movement in the midst of a life-threatening situation.
While climbing or swimming, each foot of movement costs 1 extra foot (2 extra feet in difficult terrain), unless a creature has a climbing or swimming speed."
This text is not valid for centaurs, due to equine build feature
"You count as one size larger when determining your carrying capacity and the weight you can push or drag. In addition, any climb that requires hands and feet is especially difficult for you because of your equine legs. When you make such a climb, each foot of movement costs you 4 extra feet, instead of the normal 1 extra foot."
Right. One is the general rule that applies to all creatures, and the other is a specific feature that applies only to centaurs. Specific takes priority over general.
On the dndbeyond character sheet, on speed, if you select "speed"
You get a lot of boiler plate text, which includes
"Every character has a speed, which is the distance in feet that the character can walk in 1 round. This number assumes short bursts of energetic movement in the midst of a life-threatening situation.
While climbing or swimming, each foot of movement costs 1 extra foot (2 extra feet in difficult terrain), unless a creature has a climbing or swimming speed."
This text is not valid for centaurs, due to equine build feature
"You count as one size larger when determining your carrying capacity and the weight you can push or drag. In addition, any climb that requires hands and feet is especially difficult for you because of your equine legs. When you make such a climb, each foot of movement costs you 4 extra feet, instead of the normal 1 extra foot."
Right. One is the general rule that applies to all creatures, and the other is a specific feature that applies only to centaurs. Specific takes priority over general.
My suggestion would be to just add the equine build text to the existing rule, if you're a centaur, as:
"In addition, any climb that requires hands and feet is especially difficult for you because of your equine legs."
There can be circumstances where it doesn't apply