This is always a bit of a difficulty when we talk in metaphors. After 100+ hours burn-in, I found the Bifrost no less resolving. There is in fact *more* information to go along with its resolving character, making the result sound more like real music (more "musical") and thus easier to listen to pleasurably for very extended periods (less "merciless").
At the very beginning, I found the Bifrost's sound a bit "thin" (some folks have referred to a lack of bass), and while the various instrument and vocal parts could clearly be picked out, somehow they didn't sound like an integrated whole together. This or any other subtle wrongness or lack, together with good resolving ability, can make a component sound "merciless," that is, you hear lots of detail, but somehow it's not quite right.
After burn-in, all the detail is still there, but you get the very subtle volume and phrasing changes and timing cues from the instruments and vocals that let you hear how everyone is playing together and playing off each other. Also, no more thinness - there's the full, rich sound (on material recorded that way) of real musicians and singers. No lack of bass. So there's actually more audio information coming to you, but instead of sounding even more detailed and "merciless," that detail is coming to you in its full context. There's a rightness to the sound that lets you just relax and enjoy the music rather than sitting there working to analyze what you're hearing.