Which word or phrase bwest describes the problem with clarity in this sentence?

I think Grammarly's Editor would be happier if the modifier 'in the legends' were placed after 'that' instead of at the end of the sentence.

This sentence is generally fine.

The whole sentence is twisty...

It says very little with too many words. ("support the idea that" is wordy, just state the fact!)

Try this:

"Sikorsky's logical conclusions show that very little truth exists in legends."