The problem is that there is no limit for the maximum number for a keyword.
I've just tested by creating a user with this in his bio:
asodiaosdjdjdjdjdjoasijd asidjoaisjofkbnjh21brjh12br1jh2br asdpoasdasdiiiiasdi ajsdjalskjdlaskjdlajsdkasjdd
Searching any of these words as a whole is returning a user correctly as expected.
If you are searching posts based on user Bio using the index table engine, than make sure to turn off the “Show exact matches” only option, as in that case the Regular engine is used: https://i.imgur.com/NWhIhc3.png
The regular engine cannot search the user bio unfortunately.
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