You’ll only be able to record the analog channels your Pio can tune but your TV will still be able to tune the digital ones, or at least the ones it can tune if the cable were to go directly to your TV.
IOW the Pio won’t block anything, even if it can’t tune it itself.
When you said “cable line” if you mean cable TV you’d need a QAM tuner, ATSC is only for OTA or antenna reception.
In order to record QAM you’d need something other than a CECB which will not tune QAM channels, only ATSC.
Is that what you were getting at?