Why is 185 ppi counted as HIDPI when macOS and Linux Gnome UI are designed for 108 ppi, and Windows/Linux KDE are designed for 96 ppi.
Apple has always considered 218 ppi as Retina for monitors in the products they manufacture, and Windows designed their Surface Studio at 192 ppi. Both of these allow these OSs to be displayed as designed with 200% scaling.
Gnome and KDE will also only auto-switch to 200% above those thresholds.
Exceedingly few 185 ppi monitors have ever been produced, and having owned 2 personally were never satisfactory for the HiDPI experience. In fact Gnome will auto-set 166% scaling when you plug one in.
I have also not seen a single definition outside this subreddit that sets the threshold at 185 ppi. There are some that set it at 160 ppi. Feel free to correct me if wrong.
Personally I would class 185 ppi monitors in the same group as 123 ppi and 163 ppi: significantly sharper than standard, but needs fractional scaling.