The reason people tend to answer like that is because they are constantly bombarded with posts that say dos instead of the windows command processor/batch script, with little other pertinent information as to which exact system is the target.
One thing that really tends to steam people up is requests for windows batch scripts in "Disk Op. System" forum, I believe it was given this name specifically to avoid such requests and hopefully direct them to the programming forum. None-the-less the problem persists.
Batch script can have many variations between windows versions alone(it quite common to get similarly negative responses when simply saying windows, without citing a version). It can be near impossible to answer some of the questions/provide code to work in dos as many of the commonly used commands were introduced with nt or later(like "for /f").
I agree it can be a little over the top at times, but try to answer questions in the programming forum for a month or so and it should be clear where the frustration comes from(Though from memory you questions seem pretty clear to me).
Now as to the information you posted above....
32bit nt based windows have ntvdm - the vdm stands for virtual dos machine, which runs dos programs(like command.com). Command.com isn't dos itself, just a command processor that runs in dos or ntvdm as it may be.
You may notice the copyright notices for most versions of windows extend back to 1987, for compatibility reasons programs like command.com and debug.exe were included(though probably modified).
I'll leave it up to the viewers to decide if xp has dos or not, though I believe almost all(if not all) dos compatibility has been striped out of 64bit editions of windows(so it may be true for xp 64), but be warned this is second hand knowledge to me...
Batch Variable how to