No, the arrest most certainly happened, it's corroborated from enough sources that this isn't in question, though from what I can tell the arrest report no longer exist, but there are contemporaneous notes made by Alfred Jodl. Additionally from a cursory search there are conflicting reasons given for the arrest including what you've mentioned and even communist accusations.
When I said "Nazi" earlier I should have been more precise, I was referring to von Braun, Dornberger, and his ghostwriter as "Nazis" even though AFAICT von Braun was the only actual card carrying Nazi of the bunch.
With that said, the problems with this source remains. The ghostwriter has a financial conflict of interest with the subject which would bias him to make as flattering of a portrayal of the subject, and the people involved are all intrinsically untrustworthy because well... look at the bunch... a Nazi propagandist, a Major General from the Wehrmacht, and an actual Nazi.
Look at the circumstances around this, you have the Nuremberg trials having only recently taken place which saw a bunch of dudes these guys personally knew publically shamed and hanged, These guys themselves were directly targeting civilians with these weapons, It's the middle of the McCarthy Era -- There's no way these guys could tell anything remotely close to an objective truth.
Everything they're going to say in this context is to save their skin. They're gonna write "Oh yeah, arrested by those evil Nazis for being too peaceful and science-minded" not something more realistic like "von Braun made a deal with the devil that was an absolutely psychotic and dysfunctional authoritarian regime and the deal almost blew up but that von Braun is so damn lucky he must have a horseshoe up his ass."
An adjacent topic that I've wondered about for years is his come to Jesus stuff after the war. It's plausible that he had a serious reckoning with his world view from his experiences during the war but it also seems just a little bit too convenient, you know?