Well I just did a quick test, fired 8 105mm howitzer standard smoke rounds.
Seriously injured - 7 infantry within 5 metres of impact, 2 infantry within 15 metres, and 1 at roughly 50 metres.
Numerous light injuries that I didn't keep track of.
Those results seem more acceptable to me but of course it is a very small sample.
Map was a grass billiard table 1km x 1km with a grenadier battalion minus their vehicles and hmgs and schrecks.
After the arty I rolled a sherman out from behind the spotters 8 story building and fired it's complement of WP with result that all rounds either dropped short or overshot the target by 100 metres+ for a grand total of no casualties.