There's only a need to provide a "Cutoff" and "Maxm" parameter to the SVD if one wishes to truncate. If one does not want any truncation to happen, then those parameters aren't needed.
The .position method is mainly intended to just shift the orthogonality center of the MPS without changing anything else about the MPS. So typically one doesn't want to truncate, or at least it's not the default behavior.
The SVD inside the position method is defined to just keep the same bond dimensions that the MPS had before position was called.
Finally, the .position method does in fact accept optional named args. But I neglected to mention this in the documentation. So I just updated the documentation to point this out.