Sizing madness- From DD to A cup per brand's size chart?!

I’m so confused and frustrated- would greatly appreciate any advice or guidance to make sense of this.

I’m a 32 DD. (Underbust 32, bust 37). This brand carries that cup size, possibly not in all their styles. but it’s definitely available in many items.

Yet, per their size chart, I’m a 36A which does not even exist on their website! When I select filter for sizes, there is no 36A option… not sure about in stores since I’ve only looked online so far.

So, with this kind of size chart, what’s the point in a) placing me as a size I’m not and b) not even having the size you placed me as?! Like it’s not even about distorting my size to fit your limited offerings like many brands do when they don’t carry fuller bust options. This is just… bizzare.

Why do brands do this? What size should I buy?!

Link to their size chart

Thanks in advance!