If your appointment is 30 minutes, they may decide to
do a scan or biopsy.
Do you have fibroids? These can sometimes cause bleeding when on HRT ( although you have been on HRT for two years, so not sure on that one).
More than likely, the bleeding is due to the stopping and starting of oestrogen. Any changes ( big or small ) can trigger spotting or bleeding in my experience.
Agree with Jules; your GP is following the correct guidelines. Better to be safe than sorry.
Good luck for Friday 🌺