Nice review of the Adam-12 Season 3 set, but two corrections worth noting:

The show was cocreated by Webb and Robert Cinader and is credited as such on-screen. Both men really do deserve the credit Webb's inspiration, reputation and pilot script sold the show, but it was Cinader who humanized it and gave it a realism beyond the stylistically-bound Dragnet. And as much a fan of Webb's work as I am, the season you're reviewing points this up. Cinader line produced the first two seasons of Adam-12, then moved on to develop and produce Webb's next series Emergency!. With Cinader elsewhere and Dragnet having finished production, Webb took a much heavier hand in the third season. Most of the clunkiness and stridency you note is Webb at his worst, and noticeably absent from earlier and later seasons.

It wasn't a spinoff from Dragnet, though the popularity of that show's revival drove its creation and casting. Kent McCord appeared in several Dragnet '67 episodes, in one case playing a patrolman named Reed assigned to car 1-A-12, for about 15 seconds and three lines of dialogue. Martin Milner appeared similarly with him in an episode shortly before Adam-12's pilot began filming, but the two didn't play a major role in a Dragnet episode until Adam-12 was in its second season.

Finally, not a correction but perhaps a small amelioration: someone apparently drew Webb's attention to the jaw-droppingly bad portrayals of Indians in the early part of the season. One of the season's later episodes (which you maybe haven't hit yet) takes the absolute opposite approach, casting a visibly Native American actor in a guest role without playing him as a cliche or indeed calling much attention to his ethnicity. Webb (and Cinader, again) took it a step further very quickly, casting the same actor Randolph Mantooth as one of the leads in the aforementioned Emergency!. While the new show didn't dwell heavily on Johnny Gage's Indian heritage, a number of episodes did reference it, usually to good effect. As I recall, it was recognized several times by Native American groups for being one of the few shows (if not the only) at the time to have a regular Indian character played by an Indian actor and played straight.