OK -- 2nd major edit here -- it's still not true for all of Tsojconth, but seems to hold up for most of the greater caverns, not the lesser caverns. You can find all of Tsojconth at Wayne's Books website.
Did Gary Gygax stock the monsters in Tsojconth in alphabetical order? I saw this yesterday after posting something from the 1982 The Lost Caverns of Tsojcanth, so I checked the back, and it wasn't true for the published version -- but Perkins says "the original version" of "Tsojconth," despite the subtitles reverting to "Tsojcanth."
But the monster lists in Tsojconth aren't in room order, they are just summaries.
(Sorry I can't isolate this video from a xitter link; it must be part of a longer video somewhere.)
Here are the summary encounter lists from the original 1976 WinterCon V tournament module, The Lost Caverns of Tsojconth. Not really a spoiler for Tsojcanth since the module was changed significantly before publication: