I don't understand how you reach this conclusion, if anything it's the opposite of CISC: instead of having highly specialized instructions you have a single generic instruction that can be used in all sorts of context. Note that this is very different from x86 "overloaded" encoding where a single mnemonic can have a million different encodings doing wildly different things depending on the operands, prefixes, lunar phase and/or operating mode[1], in this case there's no additional complexity to the "OR" implementation besides the adjunction of an R0 register (which is not specific to this opcode). You can still describe the encoding and functionality in a single line[2].

[1] https://svkt.org/~simias/up/20180926-112325_x86-mov.png

[2] https://svkt.org/~simias/up/20180926-112224_or-encoding.png