Why PieChart Callout is so slow?

Question

I was testing PieChart using the following random data before touching my own dataset and found the ChartLabels using the Callout function is so slow. I wonder why and is there anyway to improve its performance? I tried PerformanceGoal→"Speed" (learned from here) as the PieChart option, it seems to me not very effective. On my laptop, the following three ChartLabels option yield 0.204785, 15.0763, 48.0431 with AbsoluteTiming.

Generate data

SeedRandom[14];
list = RandomInteger[{1, 100}, 300];
stats = Counts@list
rules=Normal@stats;

Plot PieChart

Table[AbsoluteTiming[PieChart[stats, ChartStyle -> "Pastel", ImageSize -> Full, opts]],
 {opts, {
   ChartLabels -> Placed[Keys@stats, "RadialCallout"], (*okay*)
   ChartLabels -> Callout[Keys@stats, Automatic], (*slow*)
   ChartLabels -> 
    Callout[Row[{Style[#[[1]], Italic], " = ", Style[#[[2]]]}] & /@ 
      rules, Automatic] (* too slow *)
   }}]

BTW, when I changed the Head to BarChart with the rest the same, it is faster. However, the Callout slow issue remained.

—————————————————————————

Further tests on my laptop showed with specific ImageSize, the AbsoluteTiming was sometimes short and sometimes long. For example. 800 or 1000 still took long execution time (> 40 sec) while 1200 and 2000 were faster (< 10 sec).

—————————————————————————

I tried the following. In general, it was faster on my laptop.

callout=List@@@(Normal@stats);
statsCallout=Callout[#[[2]],#[[1]]<>" = "<>ToString@#[[2]]]& /@ callout;
PieChart[statsCallout, ImageSize->1200, ChartStyle->"Pastel"]//AbsoluteTiming