Nope, this is definitely a retinal surgery. Sub-retinal injections are actually done through the inside of the eye.

Your eyeball is filled with vitreous humour which although technically a fluid is really like a thick layer of gelatine, surgical instruments can't navigate that.

Before a needle is able to reach that retinal area, the surgeon must perform what is known as a Vitrectomy which is basically a chop and suction of that gelatine in order to have a good visual and be able to accurately manipulate surgical instruments.

Source: worked in embedded software for ophthalmic surgery equipment.

Some new therapies just inject a virus into the vitreous.

I don't think this is comparable. The needle must reach the retina. I am no expert but I recall the phase one trials were done to merely test if the vector was safe.

Macular degeneration is very common with 11M people in the US affected. It’s treated with intraoccular injections of VEGF inhibitors.