That depends on your definition of "HDTV", which is hugely variable, but think it obviously was.
Since they called it "HiTen", and it apears to be running on a pro wide HDTV we can *assume* it ran either in HiVsion or in a custom RGB resolution roughly equivalent to HiVison. HiVision was 16:9. Furthermore, that screen shot of in Next Gen was obviously way more high res than the 1990s industry standard 240p
By the time HiTen was shown Pioneer was selling MUSE laserdisc players which allowed for HiVision LDs. Also, while few people owned HDTVs (they were fabulously expensive) it was really common for people to own set top boxes that could tune HiVision TV and convert it to NTSC because you ended up getting a better picture that way.
So, "Hi" was very much in the mind of Japanese people as an HDTV thing, and while I can't make out the exact make and model of this monitor its almost certainly an HDTV, one that cost tens of thousands of dollars.