This is a good question. There is no good official documentation.
See my question and the answer by @Chenocq.
Also. the help page for the S2 resampling might help.
And you might be interested in my blog article about the sentinel-2-geometry-up-scaling feature in the EOMasters Pro Toolbox.
There is ephemeris information in the metadata, but I don’t know how to use them. Maybe you know. See Sentinel-2 Products Specification Document page 127ff.
