It takes a couple seconds to start the first time you launch it. Very much not instant.
What about the second time?
Then it's in cache.
Yeah, I'm confused as well. I just tried Calc on win10 for the first time in weeks or months and it opened before I could count 2 seconds. This is from a SSD where it won't have been in cache.
2 seconds isn't instant.
It's 100% instant on my computer. No delay from pressing enter and it opening.
IIRC it tries to connect to the internet in the background to download currency exchange rates