> over 300,000 rows

Any process you ever enable in code will be pushed to limits you never dreamed possible. This is exactly where discoverability can come into play - someone starts by copying 50 rows and using that to get their job done, and may never realize there are other ways (CSV export, etc).

If code can "recognize" when something like this is being done and provide documentation on other ways, it can help people learn new methods.

This is a chicken and egg problem. This limit seems impossibly high because users lack the expectation they can perform this action, because designers of software don't expect users to perform this action, because users lack the expectation they can...

I disagree with sibling comments that copy/paste is a hacky solution. It's a very natural one for lots of users and there's no actual fundamental reason not to be able to accommodate it.

There's no actual fundamental reason that opening and accessing workbook data from the command line should be so hard, either. Particularly from PowerShell.

This is a "Microsoft refuses to make composable software" problem.