Doug was talking about a two-camera interview, happens in one location and typically has good audio and relatively few takes. Yes, in that case, you often don't need timecode.
But what if it's a documentary and you're shooting 50 interviews over six months in different locations? What if it's intercut with event B-roll shot by three widely separated cameras doing dozens of stop/start takes? What if it's stand-up interviews in a disaster area and due to the stress, a camera operator misses the slate and accidentally has his audio turned off? What if you're looking through hundreds of interview files in post, and some operators had the wrong date/time on their camera? Timecode comes in really handy in all those situations.
For all those reasons (and more) my team always uses timecode, even for "easy" two-camera interviews. It keeps the procedures fresh and ensures ongoing familiarity with the devices, cables, adapters and camera timecode operation.
Regarding jam sync vs. continuous timecode, we've done it both ways, but having a continuous timecode device on each camera and recorder seems more reliable. E.g, after jam sync the FX6 maintains TC during shutdown for battery changes, but some of our RED cameras did not until a firmware update. It's easier to verify and resync the cameras using a smartphone app than revisiting each camera.
There is no "harm" from TC drift. They will drift anyway, whether TC synced or not. Even though continuous TC does not lock the cameras together, when the TC devices are remotely resynced via smartphone device or if the camera is shut down to change batteries, etc. it will usually automatically resync from the TC master. So this tends to shorten the drift period to typically around 1-2 hrs.
If the camera internal timebases have significant drift, that will exist even if syncing by audio. Most NLE audio sync algorithms use a single point on each clip. If the camera timebases are drifting, it will drift before/after that sync point on the 30 min. clip. The former Plural Eyes sync app had continuous sync drift correction, but that only applied to an audio file, not two A/V files.
It's important to do long-duration test clips in advance and characterize the drift behavior of the specific recorders and cameras. Our FX6 cameras and Sound Devices audio recorders have all shown very low drift. That assumes you don't make a mistake and intermix DF and NDF timecode between cameras. Now THAT will drift.