I understand your point. However if the ascent profile was linked to Buhlmann with GFs, the point at which you change your ascent speed would change with GFlo.
For PDC's using ZHLxxx the ascent profiles are definitely linked to Buhlmann with GF's but ascent speeds don't figure directly into the calculations for deco stops and hang times. If you look at Baker's implementation of Buhl-GF's and my own spreadsheet the formula for calculating the first stop which uses GFLo does not include ascent speed. The ascent speed affects the amount of on or offgassing and so indirectly affects the first stop depth, but the calculation itself depends only on the leading TC pressure, the m-value, and the GFLo setting.