Alan says he contributed a lot to the DS songs, and if you listen to everything from DS before and after Alan you will notice a big chance in musical terms. We also know that MK doesn´t want to share credits, and Guy had told many times that as long as MK write the song, whatever the musicians add is part of their job... that shows clearly that DS wasn´t more than MK´s band. I´m sure that Alan not only co-wrote TR (probably in musical terms only, the lyrics and main idea is 100% MK) but many of the DS arrangements during his time with the band, but, again, MK never wanted to share any credits, as he write the songs. So I don´t blame Alan for that, he is right telling he had a part on the compositions, but he didn´t assume his rol as a hired musso like Guy did/does. It´s not that Alan was arrogant, was naive, he should had assumed that his rol, even composing, adding music to MK´s song, was part of his work, getting no credit for it further than your payment.
For sure MK didn´t like Alan telling that, but this song is not only a slap in his face, it´s a "Your nobody, you never were, and you never will", totally unnecessary.