I had a TOC T240 which died in a few years.
I replaced it with a dell 1920 x 1200 U2412m.
If my T240 didnt die I would never have known how much more vivid/colorful ips panels are.
As soon as there is a good sale I will get a cheap Acer K272HULb (2560x1440).
P just indicates progressive scan, which AFAIK - all monitors are P. As far as 1200p, most commonly I think that would be interpreted as 1920x1200, however all it definitely means is how many horizontal lines of resolution you have, and the image is progressive instead of interlaced.
Overall, people just got lazy. I definitely don't want to remember WUXGA vs WQHD vs etc. I don't mind the 1200p short hand, but I definitely agree it can be ambiguous. 90+% of the time though you know what the resolution is.