I think it’s effectively that the competitors are assumed to be in a stasis field before the bell, so it’s actually the heartless sadist that rings the bell who kills Wanda, not Strange.
It’s a strange Lovecraftian Khazan version of the ‘guns don’t kill people - people do’ argument.
The stasis field may be entirely in my head though, but it would be a possible explanation we could enshrine in the starting conditions.