I've been wondering that myself. It's such a constrained space for a busway. Comparable terminals like Lechmere generally have dedicated bays for each route, plus passing lanes.
Right now, Kenmore handles about 24 buses per hour at the AM peak: 3 on the 8, 3 on the 19, 7.5 on the 57, a bit under 3 on the 60, and 7.5 on the 65. (I had no idea the 65 was that frequent - it's such a wildly peaked route, with 70-minute off-peak headways.) That works out to 960 feet of buses per hour.
Under the November 2022 proposal, Kenmore would handle about 18 buses per hour: 7.5 on the T28, 7.5 on the T57, and ~3 on the 60. Even with the 60-footers, that's about 870 feet of buses per hour. Having only 3 routes will also simply operations; currently, the 8, 19, 60, and off-peak 65 all have long layovers that require buses to be parallel parked.
If the MBTA can move the inspector parking spots and find a better spot for the 60 to lay over, then the T28 and T57 can have dedicated bays (with enough total space for two 60-footers plus a 40-footer) with a passing lane, with the 60 using whichever bay is available. That would be vastly better than current, albeit far from ideal.