This is only my humble opinion, but it would seem that the workflow could be smoother if you could create a new frame at the side of the tag so the new frame wouldn’t have a tag. This would only apply at the right edge ie. at the final frame of the tag. Inserting new frame inside the tag would combine it part of the tag.
This creates tedious process if you don’t have one non-tagged frame on reserve all times when creating the animation file.
What cannot be seen on the video is the case when you don’t have the reserve frame and you expand the animation (which you rarely do) and you would need to adjust the length again to get the desired number of frames inside the tag.
Note: I know this was probably overlooked as it was probably faster to implement like it currently works but I feel this would be improvement. This behaviour would also support my idea of the “Sequenced Tags” (Tag Sequences (Formed by ligning them next to each other)) as it eases up the creation of the non-tagged frames.