Correct. There are a few cases where the operands don't fit into a single machine word, the most notable being many cryptographic operations. Particularly RSA and ECC, which involve multiple-precision arithmetic.
There are also non-Linux cases, mostly microcontrollers. EG the Arm Cortex M0 doesn't have a hardware multiplier, the M0+ does.
And then there's that one guy who got Linux running on an 8-bit AVR by emulating a 32-bit ARM and running it on that[1]. I'd consider this a silly edge case. Too fun not to mention though.
There are also non-Linux cases, mostly microcontrollers. EG the Arm Cortex M0 doesn't have a hardware multiplier, the M0+ does.
And then there's that one guy who got Linux running on an 8-bit AVR by emulating a 32-bit ARM and running it on that[1]. I'd consider this a silly edge case. Too fun not to mention though.
[1] https://dmitry.gr/?r=05.Projects&proj=07.%20Linux%20on%208bi...