Need fare class R > 0 to book upgradeable PE?
I'm trying to put together a trip that would involve an FRA-SFO leg on Saturday, 7 September. Ideally I want to use a GPU to upgrade to PZ, but of course it's now showing PZ=0. As a backup it would be nice to at least reserve an upgradeable PE seat (better than being stuck in Econ if the GPU fails, and would improve my upgrade chances). When I try this on the website it shows a column for "Premium Economy (upgrade-eligible Economy fare)" with a fare on some options, but under details it becomes clear that none of these are actually PE fares, just various Y fares; indeed, the listed PE+GPU fares are a bit lower than the non-upgradeable PE O fares shown in the PE only column, and identical to the Econ+GPU fares. It appears that the problem is that (at this point) the flight shows R=0, and I'd need R > 0.
1. Is this correct?
2. How likely is it that this would change to R > 0 in the next few days?
3. More generally, isn't United's website basically lying by listing this fare under a PE heading?