Sometimes is easier to check the realtime motion with playback than dealing with the plots.
But MP supports this only for the .tlog (telemetry log) and not with .log and .bin from the SD card.
The .log file on the SD card includes normally more information than a .tlog.
Despite of this, MP can playback only a .tlog but not the data from the SD card.
So we need to use other tools for playing back flights from the SD card.
Sometimes there is no .tlog available (no MP connected, or connection lost).
Is there a technical reason for not playing back the dataflash logs, but only telemetry logs?
Or there was no need for this?
tlog and .log/.bin are two completely different things. Tlog is basically a capture of mavlink communication between the aircraft and the GCS, which included comm from the GCS as well. .log./bin contains far more data with a far higher update rate.
In theory it is possible to create something which resembles a tlog and playback that. But I think it does not worth the hassle. We have a very good log analyzer at https://plot.ardupilot.org where you can see log data and vehicle attitude, position and messages at the same time.