Sounds like at least in this case that ASIC in the drive was doing some (non trivial) signal processing. Would be interesting to know how hard it would be to get from the flux pattern back to zeros and ones. I guess with a working drive you can at least write as many test patterns as you want until you maybe figure it out.
At the very least the drive needs to be able to lock onto the signal. It's probably encoded in a helix on the drive and if the head isn't synchronized properly you won't get anything useful, even with a high sampling rate.
I would be surprised if it used helical recording. Data tape recorders rarely do because it's much more complex, increases tape wear, and the use cases don't usually demand that kind of linear bandwidth.
Wasn't the whole selling point of these drives that they were able to encode more on the tape than their competitors? I figure that must include some clever tricks.
