Soyuz moving, why all three?

Brian Gaff wrote:

OK, so this is more suited to the iss group, but I thought I'd ask why they
are all leaving the station to move the soyuz, surely if it blew up or
something, its better to still save one. OK pretty depressing thought, but I
thought in the past with three crew, this was only done with two people?

Mission rules: ISS only has as many humans as there are available
escape-vehicle seats.

When the Soyuz undocks, there are 0 escape-vehicle seats left on the
station, so 0 humans can stay in ISS.

If something happens while the soyuz is in transit between two ports and
the soyuz cannot redock, then the lone occupant is left stranded on the
station.

If something happens to the station while the soyuz is in transit, and
the soyuz has difficulty redocking, the station occupant may long be
dead by the time the soyuz does find a docking port that is usable.