An excellent interview and it backs up what Pick Withers has also said in the past regarding Dave Knopfler. I could be wrong but didn't John also mention it in the book (Pick and Mark the outstanding musicians but John didn't put himself in that bracket as well as Dave?)
Regarding Sid McGinnes this is old news. He played on Making Movies and some of his work is quite exciting. Expresso Love for example, superb. In regards to crediting him there are many many many albums from all eras that for one reason or another don't give full credits to the performers. Could be related to previous contracts, the way the person is paid, to protect the brand. This is probably an example of Dire Straits just keeping it simple. No need to credit other musicians if you pay them a flat fee and Sid probably appeared on numerous albums from other artists anyway. Most session musicians aren't credited anyway on albums. There can't have been any bad blood hence the excellent performance on Letterman. Suprised that the exceptional Hal Lindes didn't try to emulate Sid's parts but remember the band was a dictactorship lead by Knopfler, so he may have wanted Lindes to give something a bit different. What I will say is from the early peformances with the american in the band (1980-81) he was nowhere near loud enough in the mix. This was sort of rectified by the time Alchemy came out and it had to be during the massive Brothers In Arms tour.
Also It's actually quite common for debut albums to not feature the respective bands drummer, due to them being very green. Loads of examples, where session musicians (or even drum machines) have replaced the original drummers, but there's no need to mention it in the sleeve. Makes the respective drummer look bad or it just could be due to contactual reasons. Obviously Pick is all over the first three albums but sadly barely plays on Love Over Gold.