I am fully willing to accept the idea that different reconstruction filters with measurable differences in the audible band can sound different. It would be weird if they didn't, it's just that most people don't hear 20khz+ well or at all, so it's not usually relevant.
As for whether DACs "have a sound", that's a somewhat different, if related question. If the subjective impression isn't plausibly related to small changes in FR in the treble I'm still waiting for evidence.
Good job to Goldensound, as long as it's all true, seems like he has a combination of sharp ears and listening skills.
Also goes to show how small the differences we seem to argue about really are. You need apparently someone with really great hearing and test conditions that somewhat increase the degree of difference to hear it. At 39 my hearing is sadly nowhere near good enough to pick out differences in treble like that.