Rebalancing corridor when volatility is low (Reading 31 EOC)

On Reading 31 EOC question 9, equity volatility is going to decrease, and the answer says the optimal corridor will be wider.

Can someone explain please? I thought when volatility decreases, the corridor threshold can be smaller because the market value movement will less likely hit the threshold…

Thank you

According to CFA curriculum, higher volatility increase the riskiness of the portfolio when it moves away from optimal weights; hence, the corridor should be narrower.

Therefore, if volatility is going down then the investor can afford a wider corridor

That makes a lot of sense. Thank you