Why? K-1s not an issue if you hold forever and thus have no recapture of depreciation. Also MPCs profits vary greatly as refining business is either very very good or very bad. Cyclical. Meantime you have 5% distribution - tax deferred that is growing and with MPC about 2.5% dividend that is not growing as fast.
Do not exactly understand your post, but the sale or distribution of MLPs from an IRA does constitute a recapture for the purposes of UBTI. This issue is very complex and not well understood, but shows another reason to hold either very small amounts of MLPs inside an IRA of any flavor. The notices regarding the KMI rollup are correct and they are only going to increase when the IRS gets increased information from the companies and can match broker and MLP data to determine actual correct numbers on a sale inside an IRA.
My DW suggested that in your case the accounts were incorrectly reported by your custodian as not being in an IRA. This would cause the problem you mention and the fix is simple. Just call the custodian and tell THEM to fix their mistake. If it is the IRS's error then simply send a copy of a statement.