My experience with typing to the end of the window seemed to be that scrolling occurred when the line being typed was completely invisible.
According to
https://support.apple.com/en-us/HT201236, Command + down arrow should take you to the bottom. I used a lorem ipsum generator (
https://loremipsum.io/generator/?n=99&t=p ) to create a file a little over a half-megabyte in size and command + down arrow only moved the cursor half-way down. It appears that this does not occur when the document is edited but only when it is being read from file. Also, after you have gone to the end of the file, subsequent uses of command + down arrow will take you to the bottom.
It also appears that the documents always appear as new tabs rather than new windows. However, you can grab the tab and move it out of the window to put it in it's own window in the same way as Safari.
As mentioned in the test block, Apple needs to make changes to how bugs are reported and handled. One possibility would be to assign volunteers to various applications so that bug reports can be filtered before arriving at Apple. I'm also wondering how many of these problems are left over from the Catalina release, which left a very bad taste in my mouth as did the previous iOS release.
As bugs go, this one doesn't seem as bad as some others I have seen. You can still use the cursor bar to get to the bottom of the document. It might be an attempt to prevent you from trying to read a multi-gigabyte file into the system. It should be possible to fix this by reading the file size when you open the file and make sure that that is used as the end of file.