I've seen this article before and it is a good general rules of engagement.
Something though to remember in our new (ahem) digital age.
In yea olden days...when tape recording and large studios were the only means, it was a little easier to navigate these issues and egos. Because one would (or band would) have to spend hours often doing retakes. So it usually was obvious when contributors were spending 14 hours or even days at a time in the studio going over things, working out details, doing more than one take so the engineer could pick and choose what and where he wanted.
Also, there was strong "Union Representation" so a Union Pro Session Man was making serious $$ for just being there. If it was a long (and contracted) session hey he's leaving with a couple of grand in his pocket so no fussing.
But in today's digital age where everyone has a DAW, and specialty stuff like Addictive Drums, or Izotope most of us are more in the realm of "Creator" than "Just" a session person. (not absolute but for the most part.)
Example being...I often send out tracks I'm working on to a friend of mine in Miami who plays bass. I'm not a real good keyboard player and don't play or own a bass guitar. I use one DAW his preference is another. So often times, not only will my friend play a bass track, but he might edit for tonal quality his bass track in his DAW. His edits may or may not translate well into my DAW. Most of the time though his ideas are better (lol!) so in that role, he's more of a contributor/collaborator than just an online session guy. Plus he and I are friends and have played in bands in the past so there's that part of the equation.
Also remember that again due to the digital "sharing" age we live in...a lot of former "Session Players" are in fact moving into the "World of Audio Production." Survival of the Fittest. There's just not as much of a demand in the traditional sense of it for strictly session players. BIAB and Real Band are perfect examples of this. Although I may use a generated guitar sound from a well known/established session musician, the sound pallet generated by BIAB is going to be based on how I've arranged the chords, solos and so on. See my point?
Just food for thought. Have a great weekend all!!