I know that I have pushed the "draw" button on a VERY RARE occasion and sometimes it IMMEDIATELY awards a draw............leading me to believe that asking for a draw, after any draw rule has been effected, automatically awards it.
For a definitive answer, ask "HELP".
If the 50 move rule occurs during a game does the offer draw icon change to claim draw like it does with 3-fold repetition? I do not currently have a game in progress where this might apply.