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.