I agree that the delayed charging with the remote is hokey. But, I have a possible explanation for why it is that way.
First, I highly suspect that delayed charging function was added late in the design to try to match what the Leaf has.
Second, note that the while the timing is set by the remote, but the car keeps track of when to start and/or stop charging. That is, the remote only "talks" to the car when you press the buttons on the remote. It does not send a signal to the car when the time to start/stop charging actually occurs (if the remote were to try to send the signal at the actual start/stop time, you might have set it somewhere where the signal was blocked, so the message wouldn't get through and your car wouldn't charge).
For the system the way it is, the on-board charge controller doesn't need a clock, only a timer. And, the timer doesn't even need to be very accurate. However, to start charging at 12:30 pm every day, the charge controller would need a clock. The way it is now, it only needs to know when approximately when the set number of hours have passed.
I suspect that their charge controller was already designed, or mostly designed, when the engineers got the requirement to have delayed charging. The charging controller undoubtedly already had circuits in it that could count time, but maybe not to the accuracy we expect of a clock. Mitsubishi probably decided that adding a clock or, the user interface to set the clock, would take too long or be too expensive. Getting the time from the dash clock (radio) seems like an obvious solution, but getting two pieces of electronics to talk to each other when they weren't designed to do that may not be an easy task. Add in that these components may be being designed or produced under contract by other companies, and changes can be really hard to implement late in the game.