Understanding ArduinoJson capacity calculation assistant
If you look at the details of the numbers reported, you should see:
Data structures     112
Strings             0
Total (minimum)     112
Total (recommended) 128

As you see, there are exactly zero bytes allocated for the strings. This
means that the library does not copy the strings, and instead references
them from the character array you provide as an input.
If you instead configure the library for Stream input, it will have to
store the strings, and the capacity is then very different for these two
documents.