OK, let's both try again. I think you've demonstrated that GotoXY() or whatever works for comparatively small cursor positions, i.e. within the bounds of something that approximated a physical terminal. (25 rows x 40 cols etc.).
I'm typing while trying to monitor a machine tool on a video feed...
Leaving aside for the moment that there might possibly be an ANSI sequence for the status line (line 26) at the bottom of the screen, and leaving aside that writing to a line which is /just/ off the bottom of the screen might have the expected result if the window is then resized.
Note what I said about there being the possibility of a backing store (buffer), and note what I said about the WINCH signal (normally written in caps since that's how it's defined in case-sensitive C). That leaves the possibility that if something is to be written /way/ offscreen (e.g. your line 1000) it will initially go to the backing store, and then will be drawn onto the screen when appropriately scrolled (note that for e.g. Konsole you can explicitly set the size of the backing store) or if the window is resized to be really big (or use an illegibly-tiny typeface).
When I was checking the terminal handling code earlier I found a note that the window size is held per-TTY by the kernel, but the kernel itself makes no use of that. There isn't anything equivalent for the scroll position, so it's down to Konsole etc. to make sense of that and pull stuff from the backing store when needed... an application program can't just ask the kernel for the window position (only for the size).
Generally speaking, /something/ will make initial sizes available as shell variables:
COLORFGBG='0;15'
COLORTERM=truecolor
COLUMNS=187
...
LINES=63
but those are inherited when a program starts running, and there's no mechanism for something outside the program to update them. And that's why some things can end up in a mess if the geometry changes and they've not hooked WINCH... and this is a problem which affects plenty of programs.
And from what you've said it also affects the crt unit, but you're asking things from it that it was never intended to deliver.
Hope that clears up some of the ambiguities.
MarkMLl