[Metamorph] What's supposed to happen when you fill the gauge in Tane's lab?

It seems each organ has to be from an 80+ map to get it completely full. I very diligently farmed this but when all was said and done I didn't notice any reward out of the ordinary?

Does anyone know what the difference between it being filled or not is? I feel like I missed my opportunity to closely inspect the text to see if there was a stated difference.

I'm also curious... what does filling the meter inside the lab do?

Filling it inside maps = unique organ... but filling it inside lab (using those organs) doesn't seem to do anything.

I don't think it does anything special.
Just means more difficult & more rewards.
As far as I know

I was told that filling it in maps forces an organ drop you can put in your stash.

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ChanBalam wrote:

I was told that filling it in maps forces an organ drop you can put in your stash.

Yes, that's how you get organs to drop.