SITS has a few major problems.
First, it's a very thin movie. It's short (79 minutes), with the a lot of screen time padded by the three superfluous transformation sequences.
Secondly, it's an adaptation of the first book of T.H. White's Once and Future King series, but there's no sequel potential. The first book its lighthearted and kid-friendly, but the subsequent ones are not. Arthur gets seduced by his half-sister and unknowingly has a child, then his wife cheats on him, then the kingdom falls.
Thirdly, there are essentially no female characters other than the villain Madam Mim and the two squirrels (the older one being voiced by the same VA as Mim)
My guess is that they introduce the character of Guinevere and give her an entirely parallel story to Arthur's where she also goes on an adventure and is mentored. Arthur meets her under the guise of "Hazel" during their adventures where they share cute moments.