My home wifi AP uses channel #13 and SailfishX has no problems connecting. The command iw phy phy0 info on SailfishX says that only 2484 MHz (channel 14) is actually "disabled" (because of the "global" and "Italy" regulatory domains; AFAIK channel 14 is only available in "Japan" regulations), and 5 GHz channels 36 to 140 (5.18 to 5.7 GHz) are also available.

In the "valid interfaces combinations" it clearly shows that "AP" and "Managed" are separate features, thus the hardware does not support being both an access point and a client at the same time.

Using the command iw dev wlan0 link on SailfishX I can see it is now using the channel 13 (frequency 2472 MHz) at 72 MBit/s speed.