I find the whole GOP tax stance on IRA contributions to be far from unexpected. They are not acting as a result of any kind of deeply held beliefs, such as holding trickle down to being an unquestionable theory that works, regardless of decades of evidence to the contrary. They are responding to their "donor class" or those who are holding the puppet strings. It doesn't matter if it's whoring out to the drug industry, and creating an epidemic that continues to kill 1700 Opioid abusers ever month, repealing any attempt at controlling our totally out of control heath care industry, or proposing the elimination of any pre-tax contributions to retirement at all, to further crush the working class, while shifting more tax burden away from the 1%. The average republican siting in congress, or the senate, is there for the opportunity to "get some" for themselves. Play the game, tell the constituents that you spend every waking moment of your life protecting the unborn and removing the stains left by that illegitimate black president, and that you're still worshiping God and the NRA regularly. Then you stick your hands out, wait for the "campaign contributions" to flow, and fuck all of us in the name of greed. Oddly enough, you're pretty safe, unless you get caught forcing your mistress to get an abortion, or are overheard defending Hillary. If you can avoid that mess, the dolts will reelect you, until your wallet is full, and you want to head to a cushy private sector gig, screwing the public for even more money.
No, when it comes to proposing the stunningly stupid idea of limiting retirement funding, there are no surprises here, just business as usual.