The show doumented her last retrevial right before she was going to do treatment (initially lumpectomy) for her breast cancer, they fertilized them and then froze. When the margins were not clear on one breast they decided to do a double mastectomy/reconstruction. On the advice of doctors they decided to use a GC because of a fear that a hormone surge associated with the FET and pregnancy might cause latent cancer cells to grow. They only had 2 blasts on ice. The fact that they didn't have a lot of embies also speaks to a 37 year old using OE rather than a younger donor.
G had an earlier pg from their first IVF transfer but it ended in mc, possibly abnormal embie(?). I don't remember if the show documented that or not.
However there are many celebs who probably use DE who have not owned up to it.