Yes but that's literally how all-in betting works. That's actually the risk you are taking and the reason you usually get much better odds.
If the field was declared and that happened, you'd get your money back. It's no surprise to me to see they've altered the odds significantly of the market leaders, we're only a few days away from the race now.
So you can't get 101-1 anymore but still, 10-1 is double the quote of any other bookie about Deauville Legend, his odds have shortened with other bookies as we draw closer to the race, which is no surprise.