SYS_USleep in SCardEndTransaction in winscard_clnt.c causing slowness in Firefox

See https://bugzilla.mozilla.org/show_bug.cgi?id=1627273 for context, particularly comments 35/36. Basically, it looks like the call to SYS_USleep in SCardEndTransaction in winscard_clnt.c is causing parts of Firefox to be slow when a user has a smart card and loads opensc, which uses pcsc. Is this sleep still necessary?