As already said I was remembering a FAQ where RGB was mentionned.
I was unable to find that FAQ back at the moment, I just find similar FAQ but the layout is different.
However I was able to find back this engadget article from October 2017 where they say pimax confirmed RGB subpixel arrangement:
"Speaking of display panels, unlike the PlayStation VR, the HTC Vive and the Oculus Rift, the Pimax 8K uses CLPL or "customized low persistence liquid" panels instead of OLED. |...] It's unclear what sub-pixel arrangement has been applied to this CLPL technology, but I'll update here if I hear back from Pimax about this. Update: Pimax confirmed that CLPL uses RGB sub-pixel arrangement, which is denser than PenTile as used on the Vive and the Rift."
Also in the comments by the author of this article:
"I did mention that I'm waiting for Pimax to confirm the sub-pixel arrangement (I specifically asked about RGB vs PenTile because PSVR went with the former and it works well). But also, I did not notice any screen door effect on the Pimax 8K."
"Just confirmed with Pimax: it's RGB here, not PenTile."
That was October 13rd 2017, so yes pimax publicly promoted RGB subpixel layout before the end of the KS.
And for the argument pimax could just have discovered later it was not RGB, I don't find it correlates well with this statement from them:
"Our co-founders have over 20 years experience in display era, including many years in VR. Some of the core team members come from display industry and maintain close relationships with display suppliers. That's one of the reasons why we care about visual so much."
20 years experts in display with close relationship with display suppliers not noticing the panel is not RGB ?
Sorry for being off-topic with this, but I was pointed there was no RGB claim from pimax at the time of the kickstarter.