Atari 800 Mario Brothers - Unreleased?

Is it true that the Mario Bros. (1983) port for the Atari XL computers was never actually released?

If so, then that means there were virtually no official computer-based ports of MB at all, at least not here in the USA (prior to the 1988 Atari XEGS port, which itself was an improvement on the original 5200 cartridge port and with audio inspired by the Nintendo FamiCom/NES version of the same game).

It would also mean that the so-called "XL" ports of the game I'm seeing was just the 5200 console version's ROM burned onto other media.

The unreleased pre-1984 ports (USA):
Atari XL (just a transfer from the 5200)
Apple II (partially finished)
Commodore 64 (finished)

Pre-1984 ports of Mario Bros. that were released in the USA:
Atari 2600
Atari 5200

Post-1984 ports (USA availability):
Nintendo Entertainment System (NES) (also was a bonus mini-game within Super Mario Bros. 3)
Atari 7800
Atari XEGS
Super Nintendo Entertainment System (as a bonus mini-game within Super Mario Bros. 3)
Game Boy Advance (as a bonus game on all four Super Mario Advance titles, and Mario & Luigi: Superstar Saga)

~Ben