But even if they had tested at the wrong time, it still would have been difficult/impossible to achieve the levels noted on such low "oral estradiol" doses.
The problem of the paper is they use the term "oral estradiol" as a noun.
They are looking at historical evidence of prescription regimens and levels from their clinics database.
The evidence of results suggests even likelihood that their own clinicians were informing patients to take the medication sublingually or most of their patients followed this practice yet the paper makes no mention or consideration of such and just states "oral estradiol".
Here's the scatter chart of their patient results, i have added an orange dot to the 2, 4 and 8mg points show what a single dosage of oral estradiol should result in at trough levels.
It's notable that each time all of their patients achieved higher levels.