IV observation: am I missing something?

I'd say that you're not missing something, you're finding something.

The 'cult of near perfect IVs' feels that anything with less than a 15 attack and less than 93% (some say higher than that) is garbage. The actual difference between a 15/15/15 and a 12/12/12 in battle is very small. Further, if you're not going to power it up to 40, just power the 12/12/12 up one more level and they are about even.

The time investment needed to get perfect or near perfect IVs is a search for that last tiny scrap of ability in battle. If you fight 1000 battles with a 14/14/14, maybe 1 time in 1000 the battle will turn out differently because of the lower IVs. Of course, some people want to collect 100% IVs, and if that's fun for them, power to them and they can enjoy the game that way.

So I'd say that you just learned something.

All that said, all else being equal, high IVs are better. But perfection is not required to be very effective in combat.

FYI, right after CD, a friend and I traded our junk Beldums to each other. Of the ~40 we traded, none got lucky, but I did get one at level 30 to come out at 93%, with a 12 defense. We left 10 minutes at the end of the bonus hour to evolve, then had time to do two more trades before our final evolves. Pretty happy with how it all turned out, just wish I had a stronger shiny. But I can live with 4 strong regular and 1 good and 1 adequate shiny.

I have a 14 15 4 Shiny Metagross and a 15 11 15 Metagross, both with Meteor Mash. They are both of the same level, and the attack is the first number, then defense > hp.

I put them back to back against a Piloswine and the 2 did not survive noticably any longer or shorter.

Oooooh you're multi-accounting and it doesn't turn out the way you would like? I'm so sorry.

It allows you to turn junk IVs (that does not make bad pokémon, just a bit less good) into fair IVs, it cannot be perfect all the time. You did your best, just invest into the best you got, it's not like you've got a choice anyway. If you need one more Metagross, power up the best one you have left. Unless you really want to hunt a perfect by trading with other people.

Why would you worry about performance to the level of breakpoints against Jynx if you're going in with 2 accounts anyway? It's a trivial duo if you have any kind of leveled counters.

But indeed, sometimes the IVs don't make that much of a difference. In Metagross's case in particular, most of the DPS comes from MM, while BP is there mostly to gain energy for MM. Thus the impact of BP breakpoints is relatively small.

I would guess performance is similar due to how strong MM is.

One attack break point on a low-medium damage fast move should generally make a difference in battle. If for example your fast move makes up 30% of your total damage, and the break point increases your damage from 10 to 11 (10%) then you would expect a 3% increase in DPS.

However, if only 10% of your damage comes from fast moves (due to OP charge move) then that DPS increase is only 1% - much less noticeable.

You can argue cases where having higher IVs makes a difference but 90% of the time it's largely e-peen and just simply wanting to be "the very best". Attack IV gets the most attention since it contributes the most to total CP and in most cases where a noticeable difference in performance exists is the source of it.