"The stated benefit is that as a cardmember, you can get last-seat availability at the Standard (expensive, but possibly worth it in some cases) level just as Premier/Elite MileagePlus members would. No bait and switch. Just need to understand what Standard means."

I totally agree.

For the sake of clarity, my issue is that there are no standard awards available on my desired route ON ANY DATE, even though there are plenty of seats available for sale.

Thus, UA is not honoring their last-seat availability promise.