I heard what you heard, but did not fully understand it. It had to do with the MTO's being part of an entry and bettors having to know which part(s) of an entry would be running. It may be significant that, according to Frank D's post, the scratches were made just before 90 minutes before first post. Does betting open 90 minutes before first post? I don't know enough about the multirace betting rules to know what happens if part of an entry is scratched after betting on the sequence has begun.