williamvds's point is that the first argument to printf is still itself a null-terminated string, so it's basically turtles all the way down if you're using the C standard library.
Not quite, at least not necessarily. One feature of FTDI chips is an EEPROM that can be used to customize the enabled features, enumeration strings, and other things. That programming could probably be done in a separate jig, or in-circuit. So yes, 5 minutes of hardware work, but more potential rework at a higher level.
Not to mention the possibility of sealed cases/enclosures or potted PCBs.
Probably routed through the Mars Reconnaissance Orbiter, Maven and possibly Europe's Mars Express satellites, rather than a direct connection to the Deep Space Network
If I understood the livestream correctly, it's because they were able to (maintain|quickly establish) lock to the MRO after touch-down and zip a couple of images up through the "bent-pipe" UHF-to-high-power relay into the Deep Space Network.
Not to mention some IOT devices or cellular routers/devices might force a longer minimum cache TTL, to "minimize data usage". I worked on a device that did so (minimum pdnsd cache time of 25 hours). It ended up causing failures when our cloud server did a cut-over, dropping the TTLs 24 hours in advance. :(