Another AGM example from ex-member ah64id using his 55 amper on his pair of Lifeline AGM 6CTs 300AH :
A. 18%/80%
A. 28%/65.5% (mine with 56 amps on a pair of 100s)
EDIT--bigfootford has an example where he used 56amps on AGM and amps tapered at 68%, but I don't have his bank size in AH--must be about 200?
Wiring does matter with these, since the R in the wiring, charger to battery and among batteries in a bank, makes the bank look smaller (higher R), so the same amps seem at a higher charging rate in effect, so the SOC will be lower when amps taper.
EDIT--but not so much wiring R that you can't do the charger's rated amps.
Another thought-- if your WFCO can't quite go to boost with Flooded.
EG, on starting, the battery voltage spikes so the WFCO sees 13.3 instead of 13.1 (13.2 is trigger it says) so it stays at 13.6v
Swap to lower R AGM same AH, and now perhaps voltage spikes to 13.1 and the WFCO goes to boost at 14.4 ?