Avg. page load time is too low #17012

The metric Page load time is defined as How long it takes to load the whole page, from requesting a page until it is fully rendered within the browser. This is the sum of all previous metrics.

When looking at some of the websites reports, it seems this metric is (sometimes?) calculated wrongly.

For example here seeing this report which says 0.2s Avg. page load time but we'd expect the value to be approx 4s or 5s instead.

the "Avg page load time" are shown correctly in the report table below though:

so maybe the issue is only in this sparkline metric and how it's calculated?

The strange thing is that it sometimes seems to work correctly for example in the same instance for another website here.

(but the problem is reproduced in other instances for example here