Shots from single vs double baskets

My cafe currently has a 15g basket for single shots and 2x 20g baskets for double. If I am making a single coffee, I am told to use a single basket (15g dose) and if I’m making 2 coffees or need 2 shots of espresso, to use a double basket (20g dose).

My question now is, since the dose isn’t scaling linearly, how does this affect the quality of a single shot from a 15g dose and half of a 20g dose?

During peak periods I’m using 20g doses exclusively for either a double shot for a larger drink or 2 shots for 2 drinks. Is there a best practice when it comes to making good shots quickly. I personally find pulling a slightly longer shot with the 20g basket tastes better than a single with 15g dose but I’ve been instructed not to use 20g baskets for a single coffee.

Whats the best practice here? and where do you draw the line for the trade-off in efficiency/quality?