Browser tabs are so much more versatile than re-implemented tabbing within my app and I figured that since many people use Google Sheets/Docs/etc which also does this, then a tab per document/table/whatever would be familiar. Maybe I'm wrong. What does HN think?
Browsers tend to not automatically open new tabs though, but only if you explicitly do something to cause it.
Maybe many people do not use multiple tabs within one site/app, and that doesn't translate (There's probably some research out there on how people use browsers in practice)
Your app might look and feel too different from a browser or other tabbed environment. Does it clearly communicate where a new tab is opened, that you can't go back on it, ...?
Don’t matter. Listen to your users. Try not to argue with them. Good luck.