The rationale given for her being the unknown daughter seems quite right.
I'm curious to know why she's given two names—Margaret Jane—and what reasoning plays into assigning her as a daughter of Margaret Ogilvy, Countess of Buchan .
Without citation(s), Medlands assigned the unknown daughter as follows:
James had one illegitimate child by an unknown mistress:
2. daughter (-after 1530). m ALEXANDER Abernethy Lord Saltoun, son of JAMES Abernethy Lord Saltoun & his wife --- (-before 25 Jul 1527).
https://fmg.ac/Projects/MedLands/SCOTTISH%20NOBILITY.htm#_Toc100141807
