I consider a pity the fact of having removed 10m, 20m and 60m readers removed in S2TBX 4.0. In one side, it is a good idea to make the user think about the interpolation algorithm for up or downscaling. But on the other side, knowing that the removed readers used the nearest neighbor interpolation algorithm, it was very useful while it was possible to let images as native.
We had to remove resampling readers because there are one plugin reader per UTM zone so the number of plugins in SNAP is too big for Sentinel-2 (there were 360 reader plugin just for specific multi-resolution readers), see SIITBX-96. Furthermore for the general case (product on one specific UTM zone) it allow users to open the product directly whereas before it was necessary to choose which reader to use. 10m, 20m and 60m were added temporarily to wait for a fully functional multi-resolution product support in SNAP and this is now done. I understand your point however.