Sheets seems like a good way to get to a MVP quickly to prove the concept. If Sheets starts falling over due to demand, you know you've got a winner and its time to invest in something more reliable.
For a crisis-response, an approach may reach maximum impact within days and really only be needed for a short duration (a week to a month). Migrating a system with intense user/volunteer churn (and keeping two databases synced as you transition) can be tricky. Handling permissioning at the same time is also a challenge.
At FindTheMasks, we expected the government to have supply chains and epidemiological response (testing/contact tracing) together within two or three weeks. When that didn't happen, we kept bolting on new tools and strategies to double the lifetime of the endeavor, expecting the government to get its poop in a group by then. 20 weeks later, supply chains are somewhat improved, though the entire situation is compromised by the lack of overwhelming success at the epidemiological scale.
It's hard to go from Google Sheets to a web frontend to Postgresql and a snappy shared frontend. That is the problem statement to solve for imho (interface, schema, data portability).