According to HerHusband :
Calvin,

If it "just fits" you may be overstuffing the conduit.

Yep, my "Code Check Electrical" book says I can have a maximum of two 8
gauge conductors in 1/2" PVC conduit (for individual wires). But I'll have
four wires (8/3 w/ground) with the cable jacket. It fits into the conduit
easy enough, but I would clearly be exceeding the fill requirements for
conduit.

My main concern was whether it would be acceptable for such a straight
short run (3 feet). Doesn't seem like it would be all that different than
drilling a hole through a bunch of studs to snake the romex through.
Especially since it's a vertical section that's open at the top and bottom.

Under Canadian codes (like Calvin. Inspected/approved too), I've run 14/2,
14/3, 12/3 and 10/2 through 1/2" PVC for 5-7 foot "drops". Putting in
outlets, switches and a 30A cube heater outlet into my workshop, the
conduit is on the wall surface (not buried), and "sleeved" from the
ceiling to the boxes.

The inspector was fine with it.

That said, 8/3 sounds a trifle too far.

All you have to do is put a fitting on the end of the conduit that
would be used to attach it to a junction box, and get a
female-to-female pipe coupling to couple the threaded end of the
fitting to a threaded cable clamp. Works very nicely.

That was my plan if I have to resort to stripping the romex jacket back.
The conduit ends just above a foundation wall, so there isn't really room
to install a junction box there, and I can't really install bends in the
conduit with it being overfilled already.

Don't run the romex jacket back for running thru the conduit. If you're
going to go sheath-less, use proper unjacketed wire, with a J-box on
either end.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.