Nail placement in 3 tab seal tab shingles?



Ok I have read the directions on my Owens-Corning shingles. However
when I started to remove the existing old shingles I see they were
nailed in the tar seal strip. Now I am not sure if back 27 years ago
the installer had used nail guns. But the shingles are dried and very
bad but still I have no leaks.
Aside from the warranty being voided isn't this a good place to put
the nail for the following reasons?
1. The tar will seal around the nail shaft and the head after the sun
has done it's thing.
2. The sealing might stop the nail from popping up in the future.
3. The nail is a bit farther up from the above courses tab's lower
edge.
I am amazed that the nail is so close to the edge of the overlap
anyway when installed via the directions. I would think if anything
that the nail should go above the tar seal strip. That way any water
that might be pulled up under the shingle by capillary action would be
stopped by the seal of the two shingles before reaching the nail.
What do you think?

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