Is it safe to say but and buty are gender neutral words?
There isn't anything like a "gender neutral" word in Polish...
Or do you mean neuter? Then no. "But" is masculine. "buty" are 'not masculine-personal plural' (they are not masculine persons).
Thank you for clarifying!
Why not "Małe" for "but"
"but" is a masculine noun, like 99,9% of nouns ending with a consonant in their basic form. So it needs the masculine adjective "mały".
It offered buty, it did not offer but as an answer
Well, "but" is the only starred answer, "buty" is wrong (it could be among the words possible to click), so "but" really must have been there... we'd need a screenshot to check this issue.