Subsurface has a User Forum; there are some threads in that forum that compare Subsurface profiles with Suunto profiles; even some comments from Linus Torvald from the earlier development phase of Subsurface. You might consider posting there. On a quick read of the OP, my hunch is that it relates to the planned ascent rates, which GF's you choose for Bulhmann and/or which conservatism level you choose for VPM-B. There is a profile photo in the Subsurface Dive Planner section of the Subsurface Users Manual for planning a recreational dive to not exceed NDLs, and there is a ceiling in that profile that just barely 'clears' if the dive maximizes the NDLs.