Looking at your young white pine, Pinus strobus photos and seeing that you're in Medford, MA I'm guessing you're on the edge of the Middlesex Fells Res or near it. The Fells were my childhood stomping grounds, I lived ten minutes walking time from the edge of the Fells in Winchester nearish South Border Road. Adults said don't go there it's unsafe, a few bodies used to get dumped along South Border Rd. during the 60's, so-called "gangland slayings", convenient spot to the local Boston area Mafia types and wannabees. Those trees could tell some stories. I found the woods much safer than the street so-to-speak, and between fishing, froggin', snake/turtle wrangling and off-trail woods roaming it was my basic education.
History out of the way...
When I said put your lanyard around the tree during first ascent of an unknown conifer, I'm not worrying about Sudden Chest Rash Syndrome or anything else. It simply adds in " I will not die if my TIP blows out", that's a nice baseline. There are many ways to use your lanyard when you have concern about your TIP quality during ascent. For example I will girth my lanyard around the trunk SRT style and leave enough length to allow a couple pushes on my main line, then reset the lanyard.
If the trunk is too wide or brushy (classic case is navigating through the dead branch zone always between you and the live part of the crown), I'll attach my lanyard to something strong on the trunk. Big Pinus strobus will often have practically petrified large diameter deadwood below the live limbs, a light closed fist chop, a couple kicks, or back hand punches with the butt of your hand saw will tell you rotted or dry and a hand wiggle out from the trunk on the piece will tell you if it is firmly attached to the tree. Good luck trying to cut through dry deadwood like that with a hand saw, the rings are stupidly tight encased in hardened pitch, you'll think your hand saw just went dull. Anyway, I will put my lanyard on those from time-to-time (at the wood/trunk union).
For the lanyard uses described above I'm attaching the lanyard to my harness bridge/center not the side D's. Shock loading is always a concern (fall factor forces) with that type of use. Common sense in everything, in tree climbing we're always taking slack out of our main and backup systems when we're not doing something else. As I frequently yell at ambitous climber trainees when I seem them traipsing around a tree with too much slack, "Tighten up!"
-AJ