Setup M1 Laptop+External screen, Ventura 13.0.1, Safari 16.1:
Having the same issue and also an issue where dragging the tab off 1 window to another freezes the image of the dragged tab (not the entire window or tab contents, just the part you drag between windows) at some random point on the screen.
For example, today, I tried to consolidate a tab from one Safari window to another. The tab image dragged from one window to another, made space in the tab bar of the new window, and when I released it, it did not open in the new window, but rather the dragged tab image just froze onto the screen above the Safari window. The window I was dragging it to remained operational (can be moved, can move between tabs on it, etc.), but the tab image for the dragged tab remained frozen on the screen as a remnant until Safari is completely closed.
Absolutely terrible quality control on Apple's part here. I love the integration of Safari, but my other browsers all work more reliably. Hope 16.2 fixes it.