It’s true. Also note that you get a physical core for each vCPU with t2.
I’ve benchmarked c5 and t3 against t2 and have found single thread perf to be better on c5 compared to t2. When loading all vCPUs the performance suffered on the newer instances (each HT performed worse than a single t2), so you would get more bang for your buck on t2. YMMV of course.
Yes T2 performs quite admirably! If your CPU-bound workload doesn't use much memory, smaller sizes of T2 Unlimited can be a much better deal than C4.
T3 gives you both threads of your physical core and commensurably more CPU credits per hour to utilize them. You may notice that even T3.nano offers 2 vCPUs where T2.small has 1 vCPU.
I’ve benchmarked c5 and t3 against t2 and have found single thread perf to be better on c5 compared to t2. When loading all vCPUs the performance suffered on the newer instances (each HT performed worse than a single t2), so you would get more bang for your buck on t2. YMMV of course.