While I was writing this, I have found an explanation https://www.muzique.com/lab/buffers.htm
I know this is a different question, but I was wondering why is the source choke needed in my buffer?
I have seen other designs where no choke is in place https://www.ab4oj.com/test/imdtest/main.html
Can I leave this choke out for a broadband (HF) jfet buffer?
Yes common drain buffer has always a gain below unity, only with high load impedance and high source resistor (or current source bias) it can achieve near unity gain.