Did you read the paper?

"However, we observed a trend towards impaired performance in some cognitive tasks (i.e., attentional blink and Stroop)... future research should also explore the potential impact of microdosing on aspects of human physiology that could compromise its long-term safety."

How hard is it to come off it?

The only thing you quoted is the tudy saying that:

1) Their dose got the participants a little high still (and thus impaired cognitive tasks)

2) Their study did not investigate long-term safety

Why would you jump to the conclusion that it is hard to come off of it?

1) that's a prolonged effect, not just mid-high

2) exactly, the long term effects on a lifestyle are unknown

3) i'm asking, not jumping. personal experience and lack of long term studies