In fairness, that is probably a lot more common than you've been fortunate to have experienced.
I've been taking construction pictures for years, decades, even. I can count on one hand the times I have been challenged and confronted by an overzealous and aggressive security guard.
Sometimes the security guards will open the site gate for me so I can take better pictures. On the odd occasion I've been allowed onsite. I got a site tour of the Civil Justice Centre when it was under construction. :-)
On the whole security guards are ok as long as you don't go onsite, explain why you are taking pictures, and don't abuse them.
Sunday is the best day for taking construction update pictures. Most construction sites are quiet.
Thanks for your interesting and technical updates, Coatigan. Makes things a lot clearer.