Yes. On the DR680 channel trims retain whatever level each was set at prior to linking (referred to as channel ganging on the Tascam). The cost of that approach is some reduction of the full range of adjustment of the ganged channel set by whatever the maximum offset between channels happens to be, as once any channel reaches the max or min trim point all other ganged channels also cease to adjust in that direction, prior to them reaching the full min/max limit. That is the correct implementation IMO, as it always retains the same relative trim relationship between all ganged channels, while providing for the greatest range of adjustment under that primary constraint.
All F8 users should be aware that anytime trim linking is implemented, the previous trim settings for the channels being linked instantly changes to force them to be identical, unless the trim on those channels was already set identically. That behavior is not obvious when engaging trim linking while recording, and is not mentioned in the manual. It took me a while to realize what was happening.
32FP doesn't help me with this because I already use the recorder in that way in 24bit mode.. for the most part. I do increase trim for some quiet stuff just because, although I don't realty need to. There are other more compelling reasons..
Yes levels eventually get readjusted by ear afterward on the computer, and yes I often use the work around of linking individual pairs or subset groups rather than the entire mic-array in one set. A big reason for me is the work around of the Mid/Side monitoring issue I mentioned above. Playback directly from the recorder that includes Mid/Side decoding requires that the desired Mid/Side ratio be determined by the relative difference in trim setting between Mid and Side channels at the time of recording. Unless that were to equate to equal Mid and Side channel trims (it never does) that pair cannot be trim-linked. It would also make it easier to retain a rough mix for patchers, although that would benefit further from monitor mix levels also being linkable in the same way.