Watching a delayed show...conflicting with recording next show

This is a a behavior I don't like about the HR20. I have to explain it a bit...

Right now, I have only one tuner cabled up but it should happen even if two tuners are cabled, assuming you will be recording two shows at 9pm, instead of 1, like in my description below...

Problem:

I am recording show A at 8pm for 1 hour on channel X. I watch it delayed. I also want to record show B at 9pm on channel Y.

At exactly 9 pm, the HR20 tells me it must change channel so it can record show B. If I say yes, it dumps me out of watching show A and starts recording show B. If I say no, it won't record show B. If I say yes, I can then go into MVOD and restart watching show A, but it starts me at the beginning instead of where I left off.

So, why can't it let me continue to watch show A, since it has been recorded, and then record show B?