fwiw: cortex-m parts would be pretty conclusively referred to as 32-bit parts (due to the 32-bit address space/pointers as well as 32-bits being the native word size of the platform).

Other 32 and 64 bit platforms support some kind of "compressed instruction" support, for example 32-bit ARMv7 microprocessors (think early android phones, original raspberry pi, etc.) also support the 16-bit Thumbv2 instruction mode, though thumbv2 support was removed in AArch64/ARMv8.

This is contrasted with a "true" 16-bit platform like msp430, which has 16-bit pointers and native 16-bit words.

RISC-V also has an optional compressed instruction set for both 32- and 64-bit platforms as well.