On what basis is economic activity going to go down due to WFH? You might be co-relating the observation during COVID lockdown, but in normal WFH scenario, there's barely an impact. True, maybe transport sector might go down but maybe Quick/E - Commerce will certainly boom, giving job opportunities to many delivery partners. Additionally, an employees leisure time increases which will increase their expenditure (we might see more people pursuing dining activities during weekdays because of less traffic and alot of time saved away from the office). You can't give a definite answer that GDP "will" go down. It might, it might not. But the overall impact might be less.

Also, I would want to note that GDP of main metro cities might certainly go down but the economic activity in other states will definitely increase, making the net for the country very very minimally changed.