[GA4 Bug] Sessions started without events are not Entrances!

This is a side effect of sessions that only have session_start as an event, and is added to the cases that increase the values of (not set).

Indeed, starting with the definition of the 2 metrics:

☑ Sessions: the number of sessions that began on your site or app (event triggered: session_start)

☑ Entrances: the number of times that the first event recorded for a session occurred on a particular screen

Clearly Analytics calculates the two metrics differently, but in an ideal world the values should align because there should not be a session started that does not contain other events.

This situation could be (almost) justified when sessions straddle midnight. However, cases where a session contains only the session_start event are also found within the same day (see image).