It still uses non-y2038 internal interfaces:

130     case _PC_ASYNC_IO:
131 #ifdef  _POSIX_ASYNC_IO
132       {
133         /* AIO is only allowed on regular files and block devices.  */
134         struct stat64 st;
135 
136         if (__fstat64 (fd, &st) < 0
137             || (! S_ISREG (st.st_mode) && ! S_ISBLK (st.st_mode)))
138           return -1;
139         else
140           return 1;
141       }
142 #else
143       return -1;