I very doubt if Starbucks ever check brew ratios
They probably just work on taste at some point. They are IMHO better than Costa as use decent machines. Costa have kiosks in places and the coffee that comes out tastes totally different. Usually weak and watery. On the other hand there are outlets on each side of part of the A40 I use from time to time. Starbucks. One side has the usual the other a self service machine that offers a choice of beans. They make a pretty decent drink. I like their blond roast providing it's not made weak. Nice fairly smooth coffee. I only drink americano though. A bit like drinking espresso the taste of the bean comes through. Some beans are crap that way but milk changes it - flat whites etc where lots is used.
Ratios are a trap for new espresso machine users. They read 30sec and 1 to 2 and assume it's the only one to use. It's better to try a range. 30sec probably as something has to be fixed although people sometime move on to longer times eventually. 40 isn't uncommon but it all depends on the bean. I stick to 30sec which is pretty standard but for my wife I cut the time to 20 with the bean I use most of the time. Same grind. That is a risteretto really. based on what I drink. Run for longer and it's a lungo. I base that on commercial machines that have buttons for them. They don't change the grind size - it's too much trouble setting those up.
Ratios. A double is 60ml and standard double basket holds ~14grams. A ratio of over 4 in 30sec. Costa on motorways if you watch use a much shorter shot time.

Looks that way to me. I'd guess very fine grinding and a smaller shot size. I tried one prepacked commercial bean for hotels etc that didn't balance up until the ratio got to 4 or so. It was weak as well. Another was more like I would expect from fresh roasted, somewhere between 2 and 3 and stronger. I make my americano up to ~300ml with water. I might use a basket that can hold 20grams with weaker beans.