FTGG and "Eligible to Shoot"

The Rules Commentary says that "Unless a unit Advanced or Fell Back this turn or is Locked in Combat, it is eligible to shoot".

This means that FTGG can be used as a 'chain' units instead of just 'pairing' units. A Guided unit (that just shot) is "eligible to shoot" and is not an Observer unit, so they can then become an Observer for another unit.

Am I missing something here? Maybe "Until the end of the phase, this unit is considered a Guided unit" means a unit cant become an Observer unit later on?