It's not that uncommon. I've seen it particularly on Hawaii routes, where it will sit at R9 until T-24, and then the sweep will run. I don't think we can say for sure whether it's a glitch or just UA electing not open CPU availability until closer to departure.

In all events, if the upgrade was so important to OP, should have applied an instrument into the wide open R. Can't imagine getting so upset about a CPU.