I can confirm these pants, upgraded have a hidden effect.
The usual effect of "Courtly Measure" on the regular Bard's Cannions is, when NOT engaged with an enemy you recieve -8 STR/VIT/DEX/AGI and +8 MND/INT/CHR.
On the Bard's Cannions +1, "Courtly Measure" is, when NOT engaged with an enemy you recieve +8 MND/INT/CHR. The negative status effects are removed.