Weird - this German language source [0] from around the time of his citizenship renunciation indicated the 29 day cap last for ten years - so it would've stopped 3 years ago..
[0] https://www.tagesspiegel.de/kultur/kopflos-am-potsdamer-plat...
[0] https://www.tagesspiegel.de/kultur/kopflos-am-potsdamer-plat...
https://www.irs.gov/individuals/international-taxpayers/expa...
He mentioned it in 2013. So he's probably not affected anymore, but he still tends not to spend a lot of time in the US.