You write,

It is great that Arm will not be around to “interfere” at the trial..., and continue,...Arm is out of this case, and whether it can be sued in some separate lawsuit later on as to the ‘336 and ‘148 depends on several different factors, including but not limited to the res judicata issue mentioned above.

If ARM is no longer a party to the litigation, it surely follows that there has been no determination as to their liability ie the thing has NOT been decided, either here, or elsewhere. There is therefore NO res judicata issue.

In the event that ARM is subsequently sued it will be from a clean slate, ergo the importance for PTSC of the "dismissed without predjudice" ruling. That ARM can be sued at a time convenient to PTSC reads as a "win" in my book.

Be well