ancient specimen speed?

It doesn't really note anywhere how the Ancient Specimen works.

I measured a time of 48.3 seconds with lit workspace(as the specimen comes with light) for a normal dupe, 0 creativity skill.

However, it seems with a duplicant that has 360% total decorating errand speed, the speed isn't 3.6x faster.

The lime production is still quite slow, and it doesn't keep up with two refineries.

However, doing the math: 100kg fossil per 13.41 seconds with 80% uptime due to errand issues come out to nearly 6kg of fossil per second, or 0.3kg/s of lime, or enough to feed 24 stone hatches with sedimentary rock alone.

There is a gross inefficiency somewhere, and I'm confused as to where.