I'm in training with a extremely well regarded clinic. I cannot divulge which clinic yet. Your theory is correct that oral finasteride would be more effective and would also have a higher risk of side effects.
Topical finasteride won't be as effective as oral because oral is systemic whereas topical is localized. Which clinic claimed this? Topical can still be effective depending on absorption and concentration.
At this point, you need to be on oral finasteride and topical minoxidil. The chances of...
Any pictures from a few years back? Definitely looks like classic male patterned baldness based on those pictures you've shared. See a doctor, get your TSH checked, etc. You should definitely consider oral finasteride and topical minoxidil.