This is almost certainly empirically wrong. It's seven kinds of silly in other ways, but it also seems to have missed key recent data about the graves it discusses.
A big DNA paper published in Nature in 2022 showed that a number of burials from this period with an apparent mismatch between sex and grave goods were simply wrongly sexed. The skeletal remains looked to be one sex, but they turned out to be genetically the other. Skeletal sexing is very reliable, but not 100%. It's based on the shapes of different bones, and in a small percentage of cases it is misleading.
This is the DNA paper: https://rdcu.be/dxPqz
Gretzinger, J., Sayer, D., Justeau, P. et al. The Anglo-Saxon migration and the formation of the early English gene pool. Nature610, 112–119 (2022). https://doi.org/10.1038/s41586-022-05247-2
Page 114: "We note that several burials with weapons that were previously identified as female and discussed in the literature23,50 have turned out to be genetically male in our analysis (see the highlighted entries in Supplementary Table 1). Of note, however, a single individual still displays a sex–gender difference: a teenage boy buried with an equal-arm brooch, beads and a knife (grave 122 in West Heslerton)."
The DNA paper included over 50 individuals from the Buckland cemetery in Dover, Kent, which is the site the PhD student discusses. It's the obvious site, since it was well-known to have a few cases of apparent discrepancy between skeletal sex and gender presentation as expressed in grave goods. But was is the important word here, since the 2022 paper makes it clear that all but one of these apparent cases from all sites were misleading. The PhD student (or at least their supervisors) really ought to know about these recent results from the site they are studying.