You are right, you cannot slice audio nor play back slices in a pickup machine track. The flex machine also gives you retrigger, RTIM, sample start, etc. params that are not in the pickup machine.

As you may have read somewhere, the first track to sample with a pickup machine gets the master pickup machine, and any additional tracks that sample with a pickup machine will get the slave pickup machines. The slaves are buggy, but you can work with them if you keep the recording times on them short, never touch the Pitch param on those machines, and never slave the Octatrack to external MIDI clock.

At any rate, to use the Octatrack as a simple looper would be a waste of your money as there are dedicated looper pedals with more recording time, more features, etc. for less money. The real fun is in the Flex machine - the Flex is the reason to buy an Octatrack. The Flex is what raises the Octatrack to a higher level of creative potential than looper pedals.

Keep in mind you can assign a flex machine’s “sample slot” to the recorder buffer of just about any track. You can also assign its input to the output of any track, or to the main out or the cue out. The inter-track audio routing capability gives you tons of possibilities. And don’t forget the 3 LFOs per track - they can be assigned to a large selection of track parameters, and you can also have LFO modulate another LFO.