Fully intentional. Tour of Duty 1 is supposed to end in December alongside Operation 1 ending, not in January 2020.
And it’s relatively quick and easy to handle Marcus’ medal on Beginner. Turn on the aim bot setting, start wave 1 in Custom. Use Snub and Lancer to get headshots. Or get a Fahz in and have him hand you a Markza or pick one from a Hunter if you get Leeches at the beginning. Should take a few hours at best, but may not be very interesting.
For JD, just start wave 41 on Beginner in Custom on any map where you can funnel enemies into a single choke point for maximum possible killing. Foundation, for example. Go into spawn with the fabricator, build one or two barriers. Use remaining power for Lancer GL ammo and kill stuff until you run out. Repeat until done. Note to turn off bots on either of these two to get maximum amount of kills yourself.
For Del, it would work to start wave 50 and build as many barriers as possible. Then back out and repeat the process. This apparently used to work back around launch, mind you. Not sure about if it does now.
And these are just the fastest ways of obtaining these medals. They will not be enjoyable(as much), and rather just a grind. So if this isn’t what you’re looking for, I’d suggest you only consider these if you really won’t be able to finish the medals before the end of the Operation.