first off, AVX2 is a subset of SIMD instructions - SIMDjson includes a large number of implementations including several which do not use AVX2 at all.

next, only a subset of AVX2 instructions cause downclocking (namely, the 512 bit wide ones), which SIMDjson does not use. throwing out the use of "SIMD" entirely because you read an article about a specific AVX512 instruction which caused down-clocking might be a bit premature, no?