This will be one of those cases where the FM simulcast can't use the AM's call letters because another station is using them. In this case, there's already a KJR-FM, 95.7 The Jet playing Classic Hits.
In Atlanta, WSB can't use WSB-FM on its 95.5 simulcast because it owns an AC station in the market, WSB-FM, known as B 98.5.
In San Francisco, KCBS can't use KCBS-FM on its 106.9 simulcast because there's KCBS-FM Los Angeles, Jack FM 93.1.
In Chicago, WBBM can't use WBBM-FM on its 105.9 simulcast because there's Top 40 WBBM-FM Chicago, B96.
Interesting that iHeart has already said the simulcast won't last long. Eventually KJR 950 will switch to another format. It's 50,000 watts full time. But what else would you put on an AM signal? Why not just continue to simulcast? As said above, Fox Radio Sports gets a lot of its network shows that aren't heard on KJR on co-owned KFNQ 1090, also 50,000 watts.