There is something between 10ms and 10s, especially when it's after the initial load. The point of contention is not the website vs webapp debate, it's more that a webapp doesn't have to be that bloated.
The whole point of SPA initially was better use experience, notably through faster response time and loading.
If you are not building for the first time experience I do not understand why you would have a problem with initial load of a web app taking seconds. It's like an install just way faster. No one uses facebook only once and so shouldn't care. Android apps are so shit the "slow" webapps are still miles ahead. I do not understand why android google drive app takes 5 seconds to load
The whole point of SPA initially was better use experience, notably through faster response time and loading.