No it isn’t. Two OSM keys that “tend to indicate the same thing” should not be consolidated because of “data purity” or similar - this other thread explains one reason why (it enables detection of errors).
Another is that a data consumer may only consume a small number of keys; if a key is removed then all they can determine is “unknown”, if they don’t already check the “new one”. The original idea is well described here, and that is in no way redundant. By all means also tag surface. If you want to also tag firmness, well ATYL, so no problem there. But please don’t try remove tags to try and get mappers and data consumers to use tags that a “wiki astronaut” has dreamt up 5 minutes ago 
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