Tamiya are reusing a lot of lower hull pieces for newer kits and what you see are the remnants of the older kits Paul was talking about, but
Tamiya released as late as last year R/C kits without motors and servos as scale models so they're still doing it.
Their last two 1/16 scale kits (M1 Abrams and Jagdpanther) are just R/C models without the R/C stuff.
Upper hull looks great but lower hull are just metal tubs and bare no resemblance to the real tanks so they've had a lukewarm reception...
Some kits are still with electric motors in the kit like the
Tamiya Mk.IV e.g.
There are also signs of R/C parts in some Trumpeter (or was it Hobby Boss?) kits I've built but I've never seen R/C variants of those kits, but they probably exist on a street corner somewhere in China