What is referred to/defined as "interpolation" because as an outsider... isn't "Stable Diffusion interpolating text into images/frames/video" in a "literal" (maybe not technical) sense?
It's to be interpreted in the quasi-mathematical sense where you have images for frame A and frame B representing your data points. To interpolate between those frames, a flow of plausible images simulating the transition from A to B is generated.