Its important to note here that there is no Overhand Knot in the simple lock I mentioned. The lock is a half-hitch.
Following your picture ( "short" standing end towards left, eye legs towards right), I see an overhand knot there, around the rim of the nipping loop and the two legs of the collar...Or you had submitted the wrong picture ? Anyway, I was speaking only about the particular lock I had had described, and the things I have said were about this lock.
The fact that this wrap is not in addition "squeezed by the standing end of the bowline" says little about whether this half-hitch (and U-turn) will add security.
Hmmm. Not directly, but eventually...If there is not any self-tightening of the last knot, be it a half hitch or even an overhand knot, it will remain loose, and will be untied, sooner or later. The "lock" has to retain its own integrity, otherwise it might not be there when we will need it.
I have had no difficulty in tightening this half-hitch lock.
Neither do I !
But I suppose that you can not be permanently attached to your "locked" bowline, pulling its tail all the time, can you ? Neither can I ...
The final knot should be self-tightened, otherwise it will get loose and eventually be untied. A half hitch, or even an overhand knot used as a final lock, that has its "first" end un-tensioned, will get loose, sooner or later. The "first" end of your half hitch or overhand knot, the moment you stop pulling the tail / the "second" end, would be left un-tensioned - because it has already passed through the nipping loop for a second time, so there can be no pull transferred to this end by the loading and tightening of the bowline. Only if and when the gripping action of the nipping loop fails, in case of a sudden, extreme loading, will this end be pulled again. But the final half hitch or overhand knot could well have been very loose at that time, or even completely untied - if there is not a minimum permanent tension, pulling one, at least, of its ends.
...[any] additional "squeezing" of its tail is not required for this half-hitch (and U-turn) to add security.
the half hitch - or the overhand knot - will still be there at the time it will be needed ! If there is not any permanent pulling of one, at least. end, and if there is not any permanent squeezing of its nub, I am afraid there will be no knot left in place to secure the slippage of the collar s tail...
I repeat my last statement, hoping that I will be understood this time
I believe that, if we use [a half hitch or] an overhand knot as a "lock", its "first" end should better remain under some minimum tension, and its "second" end should better pass through the nipping loop of the bowline.