It's weird how with every single console launch people are shocked to realize that 32GB as advertised - 32,000,000,000 bytes - is not the same thing as 32GB as represented in the actual OS (32 * 1024 * 1024 * 1024 == 34,359,738,368 bytes)
It's been like this for almost every device ever released on every platform, for decades.
The Switch, much like every other device on earth with an advertised 32GB capacity, has exactly 29.80GB storage space (32,000,000,000 / 1024 / 1024 / 1024)
If there are 25.9GB free, then it means 3.9GB are reserved for the operating system, built-in software, and reserved for future OS updates which may increase the storage footprint of the device.
That's...completely not unreasonable at all.