You’re right Volk+Slit Lamp and Headset BIO are just diffrent forms of indirect Ophthalmoscopy. When people refer to Indirect Ophthalmoscopy then tend to mean Headset BIO.
I don’t know what the majority of the profession are doing now but I do know that students are taught Indirect methods and that Direct Ophthalmoscopy is currently viewed as a back up technique that you’d need to justify using (e.g small child or wheelchair bound patient). Interestingly I’ve just read a Trevor Warburton article on Optomtery Today on managing Flashers & Floaters; he makes it pretty clear that dilation + Indirect Ophtalmoscopy is required in this scenario.
I wasn’t taught Volk + Slit Lamp at Uni (graduated 1996) and only started using it routinely about 5-10 years ago. Now that I’m comfortable with it, there’s no way I’d go back to Direct. The view is massively better and dilation is required much less often. Every time I’m forced to use a Direct (and days will go by without it coming out of my bag) and shocked at how little I can see with it!