Your question was indeed confusing. The answer is also confusing.
Your have always been required to file and pay tax on UBTI inside an IRA is the TOTAL from all your K-1s in box 20V was greater than $1000. That should be old news to everyone with MLPs in or out of an IRA.
Second, if you had a significant negative number you MAY have your custodian file a 990T to preserve your loss carryforward. That is also old news.
Schwab has always put a notice about this in their statemtns as a courtesy to their clients. I received mine from Schwab and also one from TD Ameritrade this year. I did not get one from anyone else I deal with.
There is NO change in the law. Most MLPs historically have had negative UBTI, but unless I am mistaken there are going to be some big surprises this year.
There is ONE diufference and that is the IRS can for the first time match K-1s from all companies to a taxpayer. That information is then shared with some 25 states. This will result in a bunch of billed for IRAs and probably some from states as well for income tax. I have no idea how this is going to sort out. No predictions except that UBTI numbers will be much more positive and create big IRA tax bills for the unsuspecting.