I think the word “directional” can be misleading unless you understand why the term is used. The arrow doesn’t indicate that current flow goes only in one direction, but rather is used as a conceptual indication.

There are usually three conductors in such a directional unbalanced audio cable, two insulated conductors inside a ‘flexible tube’ shield. The two inside conductors are connected at both ends, tip and sleeve of the RCA type connectors. The shield is connected to the sleeve at only one end as a ‘drain’ for any captured unwanted electro-magnetic signals reaching the cable that would cause current flow. The desired audio signal travels via the two inner conductors just as well in either cable direction/orientation. The question is, at which end do you want any stray currents to be drained?

If both the source and destination devices provide equally able drain for stray shield currents without interference with the intended signal, then the orientation of the cable is not a concern. If you obtain better rejection of interfering signals by having the cable in one orientation or the other, then choose the better orientation. If in doubt, follow the manufacturer’s instruction.

As to break in, there have been thousands of words posted on this site on that topic, both for different types of equipment and for cables, with a whole spectrum of ‘believers’ in one idea or another. IMHO, irrespective of the usual audiophile publications’ opinion of income-aware ‘experts,’ human acoustic pickup and brain interpretation is likely much more subject to change over time than a properly constructed interconnect made from reasonable materials, whether you paid $20 or $20,000 for that interconnect.

In the end, if the system sounds great, don’t sweat the arguments, just enjoy!