This is true and yet over the years in syndication these contracts never prevented the airing station from monkeying with them to make room for more commercials. Most notably the use of time compression but I recall times stations would cut the opening theme and the credits out altogether.
But simply not showing the credits is not the same as altering their content. Also, I think that when TV stations fail to show the credits (legibly or otherwise), that's technically a violation of their responsibilities. I can't cite a source for that belief, though.
Also, I doubt those 1960 contracts would hold any sway over credits as they appear on DVDs as they didn't exist back then and weren't covered.
I think that logic is skewed in a number of ways, but I'm not certain how.
Besides, what would be the point? Kelley wasn't actually a regular in the first season. He appeared in most first-season episodes, but he wasn't in "What Are Little Girls Made Of?" or "Errand of Mercy" (or "Where No Man," of course). In the first season, Kelley was a recurring player who just happened to recur an awful lot. That is the truth, and the existing credits reflect that truth. It would be dishonest to alter them.
No matter how the industry butchers the word "remastered" to make it apply to these new works of art its not even clear Paramount is avoiding new contracts in creating them.
The industry doesn't butcher the word; fandom does. The term was applied quite accurately; a remastered release is one that is printed from the original master copy of the film for maximum quality. Specifically, this release was digitally remastered, which means making digital scans of the original color negatives (I believe) and digitally recompositing them for maximum image clarity and authenticity of color reproduction.
In addition to the digital remastering that gave TOS Remastered its name, it had its visual effects replaced with newly created CGI. Because of this, bizarrely, fandom somehow started misusing the word "remastering" to mean "updating the effects," even though it's been a standard term of the industry for decades and everyone should already be familiar with it.
And "avoiding new contracts" has nothing to do with anything. I'm pretty sure that DVD residuals are something that's negotiated separately anyway, considering that raising them was a big sticking point in the negotiations that led to the recent WGA strike and nearly a SAG strike. So if you're proposing that retroactively adding Kelley's name to the first-season main titles would bring his estate more residuals on first-season DVD sales, I think you're wrong that there'd be any connection between the two.