It sounds like you're zeroing in on a great load.
Chrony's don't report on group size/accuracy. But, they have their place.
They don't even have to be terribly accurate to be useful. While the readings are affected by lighting and other conditions, relative shot to shot measures are pretty good.
As such, your chrony may register 2715, 2700, and 2730 fps for the same load travelling at the same MV on three different days. But, if you fired those 3 shots within a few minutes of each other, you may well find them to be within a few feet per second.
As such, a given shot string with low SD and ES is fairly certain to have low SD/ES even though the actual velocity may be +/- 15 fps from what was reported.
And the more samples you collect, the more confidence you'll have that the trend will continue.