The output impedance of M5 is 0.18ohm
Yes, but there was a lot of confusion with M2, M3, and M5 because Shanling used different testing and/or reporting methodology than other DAP manufacturers. This resulted in much higher output impedance being reported on product release. Once Shanling started using the same testing methods as other DAP manufacturers, corrected output impedance values were released which were much more in alignment with other DAPs released at that time. Unfortunately, the earlier, incorrect information stuck in people's minds even though the corrections were posted here on headfi numerous times. This led to many people avoiding what turned out to be excellent DAPs.
The only one that didn't drop to 1ohm or below was the M2, which is around the same output impedance as the M2s. I have buddies so tried M2 with their hybrid or multi-BA IEM and didn't like the results because frequency response was noticeably altered. In the other hand, I have some other buddies who ended up preferring their hybrid or multi-BA IEM with M2
because of the alerted frequency response - feeling they for a boost in bass response, clarity, etc. To each their own.
For my part, I'm lucky to have access to many IEM and have a quick & dirty measurement rig for IEM, so I can help people out by showing them FR curves with a 1ohm OI DAP vs M2 or M2s with ~5ohm OI.
And the Shanling M2 series are by no means the only DAPs with higher OI. For instance, Soundaware DAPs have ~10ohm OI...