There is enough contact are that I doubt it could ever come apart. The welds and surrounding surfaces look so clean it almost looks like mig
But 120 amps with 1/8" rod on 1/2" plate seems low to me, part of the weld looks like good penetration but some does not. This is assuming it's a single pass? like I said though even subjected to abuse I don't think it would fail, due the total amount of surface area welded.
If that were me with 1/8" 7018, I would probably be somewhere close to 140-150 amps, then you will see the penetration.
Like you mentioned though we are never sure how accurate our dials are, I actually do suspect mine reads higher than actual. That or my old welder read lower, cause they definitely don't corelate.
Just an amateur's opinion,
JB
I'm another amateur welder, so don't feel like you're alone here

Thanks for the compliment about MIG, I wish my MIG welds turned out like these.
According to ProStar's application chart, the 1/8 7014 is designed for 100-150 amps, with 120 being optimum. Their 1/8 7018 can be run over a slightly wider range from 90-160 amps, again with 120 as optimum.
I may be wrong in my thinking, but I usually try to set my current to run the particular type and size of rod I'm using.
I look more at the toes of the weld to see if I'm getting good penetration, to me high toes mean the weld is cold. Undercut and excessive spatter/glowing rods means too much heat on the other side of the equation.
I choose the rod size based on material thickness. I try to use 3/32 for anything under 1/4 inch steel, and 1/8 for anything heavier. My welder is limited at 140 amps, so material prep and multiple passes has to take place on heavier stuff. Not much call for me to weld anything over 1/2 inch plate.
As an example, if I try to run 1/8 rods on 1/8 plate, in order to make them run well the current setting is high enough that I have trouble with burn-through. 3/32 works a lot better for me on thin stock.
I'd sooner match the rod to the material and run it at the right heat for it to work well.
I've almost stopped "weaving" welds these days, unless it's non-critical and I've got a big space to fill in. Weaving hides a lot of sins IMO. Running a slower hotter puddle and letting it do the work seems to be working better.
Sean