Therefore a question to Andy : Is there a relation between -dvd-compat with DVD+RW and not experiencing missing bytes at the end of the written part of the media ?
In legacy DVD-ROM unit only. You can find a unit which will mount media with "misplaced" lead-out (in other words recorded without -dvd-compat) and then hit virgin surface, which will most likely get you into trouble.
(I understand that -dvd-compat puts the leadout at the end of the data area.
Also keep in mind that lead-out is moving one way, toward outer edge to be specific. Most notably if you zap a recording with smaller -dvd-compat one, lead-out remains where at largest boundary.
But does that mean anything for readability of the data's tail by the common Linux drivers ?)
"common Linux drivers" rely on value returned by READ CAPACITY command. The value most commonly coincides with lead-out position and is believed and was observed to be accurate for DVD media. Draw your conclusions. A.