The part about a pot trust that I find most interesting is the application (or lack thereof) of the separate share rules [IRC §663(c)]. I find it interesting because I still struggle to understand the separate share rules.
On the one hand, any trust for the benefit of a single beneficiary will never be subject to the separate share rules. However, I fear that most other trust or estates (with multiple beneficiaries, who are all supposed to be treated equally) should be applying the separate share rules when allocating DNI and the potential need for equitable adjustments.
In the best case scenario, all distributions are always kept equal (within each tax year). But anytime unequal distributions are made, the separate share rules require special consideration of the distribution of DNI (and therefore IDD).