Everyone has a story or a preference with Genesis early or later. With regards to "The Lamb" i would say it's in there with the best Prog albums ever recorded. Lyrically and musically stretching the envelope. A close friend of mine was a singer in one of the most popular Genesis tribute band in the world and has a lot of insider knowledge due to meeting and playing with some of their past members. I can confirm that in addition to the quote mentioned in the OP that there are numerous other lyrical references on the album to Gabriel's unrest within the band at that time. I can't think which ones they are off the top of my head as it's been some time since myself and friend chatted about them.
There are some great FB Genesis groups worth seeking out which i believe have ex Genesis roadies and associates as members. They share anecdotes and rare pictures. Well worth seeking out chaps.
https://www.facebook.com/groups/621442347936242
https://www.facebook.com/groups/347574972407269