But only on one band (27MHz). Everywhere else it's not a half wave.
CORRECT. Throwing tuners at their base don't make them 80-10 Multi-band verticals.
The original Cushcraft AR-10 is also a 1/2-wave vertical, that uses the tuning ring for matching.
They even sold a CB version, AR-11, for a short period.
The Cushcraft R-3 was the 1/2-wave AR-10 vertical,
with a motorized capacitor and 2 fixed capacitors for matching 20, 15, and 10 meters.
Add L-C traps; matching box with 1:4 and choke balun; 0.05-wave counterpoise wires --
you get the Cushcraft R-4, R-5, or R-7 Multi-band verticals --
and later the clones: Hy-Gain Patriot series (AV-620, AV-640).
Point being ... all these CB/10 meter verticals are "one band wonders" -- as you stated.
IF you want to make them Multi-band, it requires adding more parts and aluminum :-)