I don't get it. All the documentation links posted say it has to be 1 and 1 for memory-optimized tables. The example posted above shows an error message stating it has to be 1 and 1. The code in the question does not include WITH(MEMORY_OPTIMIZED=ON) so technically anything could be used for the IDENTITY in just that fragment. But it is stated that memory-optimized is the intended goal and that fragment is not terminated with a semicolon. One would assume that WITH(MEMORY_OPTIMIZED=ON) is the next line after the code shown.
So where is the evidence that anything other than (1,1) works with memory optimized tables?