From an FR perspective, I'd say the issue is that some planars have these resonant dips starting from the lower treble and going up at the harmonics, which apparently change wildly with even minor variations in positioning:
Based on measurements, non-stealth egg-shaped Hifiman headphones also seem to exhibit this behavior. My guess based on the CSD measurements I've seen is that the cause is the planar drivers being either deliberately or inadvertently underdamped and allowed to ring freely.
Based on my subjective impressions, including listening to sine sweeps, of several Hifiman headphones, I would say that the ratio of the depths of these notches correlates with staging depth, imaging coherence, and bass slam when they're positioned on an ideal spot on my head but with all sorts of timbre flaws and imaging wonkiness, particularly hollowness and tall staging, when it's even slightly off.
My guess is that the Timeless's perceived soft presentation is caused by the 5- and 10-kHz notches being too deep at certain insert positions relative to the air region, letting too much high-end shimmer "shine through" and overextending the trailing edges of transients. My prediction is that it would be resolved if you appropriately EQ'ed down the frequencies from 13 kHz up.
Based on playing with EQ, I'd say that bluntness is usually caused by insufficient energy at the right end of the upper treble notch, typically at around 12 kHz, which does not seem to be a problem with the Timeless.