Who would ever realistically compare a 8 core CPU with hyperthreading against a 16 core CPU (hyper threading or not)? Also the article makes it sound like the cost of a 8x x86 CPU(with HT enabled) is same/similar as a 16 x x86 CPU VM. I assume this is not the case(I have never used Azure, the fixed allocation models of all of the big public clouds have been a big turn off for me starting ~12 years ago so I really haven't paid much attention to them over the years).
Things would be a lot simpler if they just spit out some numbers from some benchmarks to compare the systems. Benchmarks are of course questionable by themselves but the performance claims being made here seem even more vague than benchmark numbers.
However if a single modern ARM CPU core can compete with a single modern X86 CPU core in server workloads that would be interesting, historically anyways it seemed ARM's designs were for just tons of cores on the chip(more than the standard x86 anyway), as an aggregate they may very well be on par with x86 (historically again they have had similar power usage from what I've read, that being 150W+/socket), but you're not comparing core-to-core performance( because the chips don't have the same number of cores - which in many cases doesn't matter I just mention that because the article seems to focus in on core-to-core performance).
Never personally been a fan of hyper threading myself mainly because it's not easy to assume how much extra capacity those threads give(but I haven't disabled it on any of my systems I just measure capacity based on actual cores rather than some funny math to adjust for extra threads).