I'm looking at the piece in the Instagram post linked by the page, which begins, "honor of holding in their service". The lines are so straight, the letters are so uniform!
I also remember teachers telling you when writing cursive to seldom lift your hand from the page. I think that act of keeping your pen on the page for most of the writing process encourages a smoother and more natural flow, reducing the chance of jerky, uneven strokes
A lot of bad handwriting stems from using it to write down things quickly (see: https://imgur.com/doctors-strike-5ANma ).
If you instead focus on doing slow calligraphy, your handwriting can improve rapidly.
I highly doubt most people could write that well
> Sheldon Richman quotes data showing that from 1650 to 1795, American male literacy climbed from 60 to 90 percent. Between 1800 and 1840 literacy in the North rose from 75 percent to between 91 and 97 percent. In the South the rate grew from about 55 percent to 81 percent. Richman also quotes evidence indicating that literacy in Massachusetts was 98 percent on the eve of legislated compulsion and is about 91 percent today.
Any reason for this being an American thing?
I'd still assume fine penmanship was a mark of the upper class though