You are completely right. This was an issue many of us (certainly me) spent a lot of time trying to get sorted. It is sorted. If your broker withholds 15% on DIVIDENDS not TRUST DISTRIBUTIONS in a retirement account, just shift those assets to someone who does not.
I hold a lot of PSN and MMT at Interactive Brokers with ZERO withholding (at least on PSN since MMT hasn't paid a divi yet).
The real remaining imbalance is the inability of US investors to trade Canadian options, while the reverse is possible. So we can't hedge as effectively.