You're right, but it's not going to be an easy fix. The game tracks if you've witnessed the explosion (without being caught in it), but not where you were when you saw it. I'll see what I can do for the Strabo update though.
Huh. As an ameteur coder myself, I thought this wouldn't take much effort. Unless I'm mistaken, that's the only use for the tracking? If so, you might be able to create 2 bools for both the dam and halfway to astrape, and add/change each one when they change. Or you could expand that to 2 messages, as it would be welcome to know specifically how large the blast radius is.
In principle, yes, until you consider that the log for witnessing the explosion is already one of the top 3 most complex logs in the entire game (alongside the rover out of power and drinking the first water bottle logs). There are I think ~16 different variants for witnessing it from different locations/distances, while travelling in different ways, and if/how many times you've witnessed/died to it before.
The actual of adding a new log for witnessing it from one side or the other, and tracking that with a flag would be incredibly simple. Making sure that none of the existing logs get shown when one of the new ones does, and that neither of the new ones overlaps with any of the old ones will be a significant task.