Hmm, it could absolutely be either/or in this instance, but I think i'm going to assume that it's me not liking the sound because I don't dare assume it was just the pair and then I end up buying them and they actually sound like that to me.Depending on how new that pair was (or how abused they were by other folks who've demoed), it's possible that the driver could be damaged or in need of a little break-in. The CX400BT were a little rough out-of-the-box, too. Most of these DD-based TWS will have a similar problem. Not to open the whole "does burn-in work" can of worms for the umpteenth time, but I'm sure I'm not the only one who's had this experience.
But if you didn't like the sound, I don't blame you. Took a while to grow on me (just like the HD650/6XX did), too. You may need to acknowledge that your ears either prefer balanced with an earlier treble roll-off or there are upper midrange spikes (3k/7k/8k) that you potentially would have to EQ outside of Sennheiser's app, which for the life of me, I can't find an EQ setting that my ears appreciate that doesn't also add in distortion.
To me the treble really just introduced a whole bunch of sibilance that messed with my ears way too much to be enjoyable overall even if I didn't mind the rest of the sound too much, but I think I prefer slightly warmer sound with more bass (but not bloated) with highs and mids that are still detailed and clear, but without any harshness or sibilance.
I think that the Sony XM4's will be more my vibe, but with that said probably not my thing all the way.... but for a lack of other alternatives that i've tried i'm pretty sure I will at least think they're GOOD even if I don't end up loving them.