I've picked common first and last names for this example, but it seems to be generally true that WikiTree is unbelievably strict when searching on first names while at the same time being unbelievably permissive when searching for last names.
Say you are looking for Charles Smith on behalf of a daughter born in the 1930s. Your only clue is that he was born somewhere in the Midwest. There are literally thousands of Charles Smiths, so you say date of birth 1900 give or take 12 years. There are still over 500 hits. She offers the help that he was called Charlie, not Chuck or whatever. There are only 130 of those. You patiently work through the list, and establish with her help that none of them fits.
"Sorry, dear, but your dad seems not to be on WikiTree."
But if it had occurred to you to search for Charly Smith, you would have got him straight off.
Now actually I wasn't looking for Charlie Smith, I was looking for Molly Bergh. I was offered people with the exact name or nickname Molly and surname anything from Berger to Burke, including one Molly Bergh but it's the wrong one — but I was not offered Mollie Bergh, which is the right one. (I'm still no nearer to finding her formal first name, which might be Marie).
Maybe the search options could include an option on first name variants too.