It seems like an inference from correlation that someone extrapolated out in a linear fashion.
In isolation, I don't think that 100ms in delay before paint really causes enough impatience in people that you'd lose 7-8% as a direct result. Humans don't really make that kind of decision within such a minuscule window of time; to a degree, we expect our devices to have delays.
More likely, that loss of conversion is correlated because sites that have longer than 100ms latency have latency that's extreme enough to reach the "I give up" threshold. A site where its pages take 3 or more seconds to load would see a big difference, but that doesn't mean that a site with exactly 100ms latency will see any meaningful loss of conversions outside a margin of error.
People will also be much more patient with a high-value site. For instance, I'm willing to wait a few seconds for each page to load on the McMaster-Carr website because it's an otherwise good experience and a high-value store. But I'm far less willing to tolerate delays on some horseshit Shopify page plastered with ads and reselling crap from Alibaba. And if you've got a blog that's poorly formatted and overall signals low value content, I'll dip out the moment I detect the slightest monkey business slowing things down.
In isolation, I don't think that 100ms in delay before paint really causes enough impatience in people that you'd lose 7-8% as a direct result. Humans don't really make that kind of decision within such a minuscule window of time; to a degree, we expect our devices to have delays.
More likely, that loss of conversion is correlated because sites that have longer than 100ms latency have latency that's extreme enough to reach the "I give up" threshold. A site where its pages take 3 or more seconds to load would see a big difference, but that doesn't mean that a site with exactly 100ms latency will see any meaningful loss of conversions outside a margin of error.
People will also be much more patient with a high-value site. For instance, I'm willing to wait a few seconds for each page to load on the McMaster-Carr website because it's an otherwise good experience and a high-value store. But I'm far less willing to tolerate delays on some horseshit Shopify page plastered with ads and reselling crap from Alibaba. And if you've got a blog that's poorly formatted and overall signals low value content, I'll dip out the moment I detect the slightest monkey business slowing things down.