For the economy, 0+7 is actually worse than 3+4. If it is 0+7, Hong Kong locals will flock to Japan, but tourists will definitely not come to HK. Under 0+7, tourists can't go to restaurants and other indoor places, why should they come to HK?
In the end, with a large number of local people traveling abroad, the local economy of HK will suffer a lot of losses, but there will be no expected number of tourists to compensate.
If they want to lift quarantine, make it 0+0! There is no point in imposing +7, what will the government do if a tourist tests positive during +7? Send them to quarantine facilities and not allow them to leave HK? Who would be so foolish to take such a risk to visit HK? No way, totally pointless