Correct. The Soviet technology for growing diamonds is HPHT (high pressure high temperature). There are a handful of known producers and research facilities in the former Soviet Union that can grow diamonds, but all using HPHT. These were all industrial grade until the late 90s-early 00s, and colorless diamonds did not consistently grow with this technology for several more years.

The other technology you mention is CVD (chemical vapor deposition), which was not developed in Russia, and was not commercially viable for gem-quality diamonds until the last decade either.