I was able to get my blueprint print nodes to show up in packaged Development builds’ logs if I adjusted the print threshold for LogBlueprintUserMessages in the project’s DefaultEngine.ini:
[Core.Log]
LogBlueprintUserMessages=Verbose
I’m actually not 100% certain why this works, but looking at KismetSystemLibrary.cpp I would guess that packaged builds must hardwire bPrintToLog to false, which shunts the UE_LOG calls to print at the Verbose level rather than Log.
EDIT: I will say that my situation might be different than yours, as I WAS seeing printing to screen happening, but not being added to the .log file.