This behavior I see throw the patchs:
All artillery units with barrage ability (Sherman calliope, CW Let and Cap, Priest),
also tanks during HE shot (CW Sherman 17pnd, CW M10, CW Canadian Shermans, USA Shermans and M10)
don't become auto targeted by enemy units.
Just look at German TDs within range of fire during ambush mode or Panthers or tank hunters infantry in ambush mode vs Sherman Calliope when it starts to rocket barrage.
100% same behavior vs all this ^ units