Thread:Extension talk:InputBox/preloadparams Doesn't work (version 1.24.1)/reply

You're not going wrong, but apparently support for  was added for the 1.25 version of InputBox and it's not present in 1.24

Doing a grep of the code of 1.24 doesn't match anything for preloadparams, but for 1.25 it does. I've fixed the compatibility column.