It will adjust pH down. Activity will be reduced. This is what OP is after, so this particular mode of 'out of whack' would be desirable here. There's nothing really that will topple over or go catastrophically wrong when reducing the pH by this limited degree. The main downside is that the reduction in activity may be difficult to predict, although I'm sure there's some tables or charts here and there showing the relationship between pH and developer activity for a PQ system.
Since ID68 is already a boric acid/borate buffer, adding more boric acid will simply set the pH to a slightly lower value. Given that it's a buffer system, the effect won't be dramatic. I plugged the numbers into Copilot and it comes up with a drop from ca. pH9.0 down to pH8.7, which seems plausible to me. This can/will still constitute a significant difference in activity. Copilot gives a tentative guess of a 15-30% reduction in developer activity, which again seems plausible to me.
Of course, the net effect is the same as simply developing ca. 20% shorter as OP was already doing, hence the earlier suggestions to that effect. The advantage of simply reducing development time is that it's an easy and intuitive change in the process that has the desired effect and can readily be scaled up or down as desired, without any risk of gross non-linearity due to a buffer system running out of steam, non-linear pH-activity relationships etc.
