Not anymore. Have you seen Gemini 2.5 Pro? Ask it simple questions and it almost doesn't "think". Ask it a coding question and it'll write a long reasoning article. I think the same goes for o3.
"how long break distance does a train need if going in 100 km/hour?"
Just need a quick reply and you dont care so much (maybe showerthought)? Or is life and death depending on the answer?
The same question can need different amount of thinking.
In this situation I suspect you'd still want the answer quickly.
If you need the answer within a couple hours, you can probably get it for an expert; if you need to get an actionable answer within minutes, based on some back-of-the-envelope calculations, then a SOTA LLM is a much safer bet than flagging whoever seems the smartest in the room and asking them for help.
Definitely, in my experience. Elsewhere in the thread, OP says that open models/systems don't do this, in which case this seems like important work toward making open alternatives competitive.
You could even put a simpler AI in front to decide if it was effectively the same query.