Noting that, in recent times, the website has not always successfully processed upgrade requests of this nature. I've had to make a few calls to SST to have upgrades manually processed and they have mentioned the website seems to have a bug at the moment.Yes that’s correct. If U is available (a regular Domestic Business Class Award) at the time of you requesting the upgrade then it will get confirmed immediately and points deducted.
It’s easy to check this online before buying your ticket.
Further U seats may get released closer to departure.
Worked to my benefit in at least one instance, with one of the requested upgrades never queued to the FFSC for charging of points