Maybe it’s just me but lately I’ve been noticing a lot of sentences worded like:
when it seems the sentence would be perfectly clear written:
Is there some rule of grammar I’m missing in this case or perhaps this has always been convention and I’m just noticing it?
It’s not an error or rule. It’s a style.
Sometimes people just prefer to write in inefficient ways.
One has a dependent clause with an explicit subject and the other has an implied subject. Neither is wrong. Just because a word might be unnecessary in some absolute sense doesn’t mean it should be discouraged.
I use ‘what’ and ‘that’ and some others too frequently just to make sure what I’m writing is clear. Some of it is from technical writing where pronouns can just confuse everything. Some of it is simply laziness or haste so I don’t have to start a whole sentence over again.
What you’re overlooking is that you can only get away with this when the noun clause is the complement of a comparative structure, because more than gets assimilated as the head word of the clause. If you are using the noun clause in a non-comparative sentence, I don’t think it would be considered grammatical, (though it may matter whether the what is the subject or the object of the clause).
Compare:*A) We need to know more than what is happening right now.
B) We need to know more than is happening right now.
**C) We don’t know what is happening right now.
D) *We don’t know is happening right now.
*You could say B, but I doubt you would omit the what as in example D and say that it is “unnecessary.”
Yes, though it’s actually the object of the noun clause. It makes a difference, because in adjective clauses we often omit the object relative pronouns, but not not subject relative pronouns, and I believe what the OP is doing by omitting what is a kind of mimicking of that pattern. Again, though, it only works in comparative structures.