Well, actually... ;)

The 68k only has a 16-bit ALU, so at the core it's a 16-bit CPU despite the 32-bits wide registers.

Depending on what "is" is... It's a 32 bit architecture, what do you care if it is implemented with 4 or 16 bit microarchitecture. Some minicomputers were built from bitslice (1-bit) parts :)

It has a 32-bit instructions and internal data bus too, though. :)

The Z80 has a 4-bit ALU but no one calls it a 4-bit CPU.

Does that mean it was faster at dealing with 16-bit values even if it had 32-bit registers?

Hmm, looking at cycle count tables it looks like 8- and 16-bit operations are indeed faster than 32-bit operations (e.g. add.w is faster than add.l).

Deterministic CPUs seem like such a distant part of the past.

I loved the days when Motorola and Intel would ship you a full set of detailed manuals about everything from CPUs to MMUs, UARTs and whatever other chips they made. I still have my Motorola manuals sitting on the shelf. Was such a nice instruction set to learn on after the 6502.