It doesn't have to be a turnover. In an 18 ac "pond" that has a max depth of 8' that I used to manage, they had both summer and winter kills. The HOA didn't have a large enough budget to allow installing an aeration system in the whole pond, so we did 1/2 of it. The next year they experienced a summer kill in the half of the pond that was not aerated........ Visibility was around 18" at the time, and this is the year following a summerkill then a winterkill.
So to me, aerating even a relatively shallow pond will help minimize fish kills due to low O2 events.