After I re-checked, I must slightly modify my original post. The unit in question is not 3-phase input or output. It is actually a single-phase 208V input and 208/120 single-phase 3-wire output. However, this doesn't change my original question at all.
If anyone cares to investigate, the model is APC SURT15KRMXLT-1TF10K
Input: 208V single-phase with NO neutral connection (2 x Hots, 1 x Gnd)
Output: 208/120 single-phase (2 x Hots, 1 x Neutral, 1 x Gnd)
Literature notes the unit is a "transformer-type", but does NOT say whether the internal transformer is on Input or Output. The O&M manual does not provide any further information either. Where the heck does the Output Neutral come from with no incoming Neutral? How can it not be an SDS if it is a "transformer-type".
When I contacted their customer support by email, I was told in no-uncertain-terms that NO Grounding Electrode Conductor was necessry because that was obtained "from the upstream supply source". Mechanically, there isn't anyplace to connect a GEC anyhow. It obviously isn't designed for it.
If it had an incoming Neutral, I understand it could be a NON-SDS unit. But it doesn't have a Neutral.
Since it has a transformer, it would appear to be a SDS. If it is, the Output "could" have an Equipment Bonding Jumper inside the unit . . . . . but what about the lack of a GEC? The thought occurred to me that they "might" simply bond the Neutral it to the Incoming Source Ground conductor. But that certainly doesn't meet NEC and I wouldn't think it could get a 3rd party listing if that was done.
My IEEE Green Book (Std 142) has an entire Section devoted to the subject of UPS System Grounding (Section 1.9 in my book). It shows (and explains very well) eight different arrangements of UPS grounding & bonding. All of the eight IEEE examples make sense to me as far as NEC is concerned. None of the eight examples seem to fit this unit. It's listed by numerous international third-party agencies.
To me, it doesn't seem to be either Non-SDS, or SDS.