Burn the witch!
Lets read through that page for a second though:
Drop support for obsolete HTTP versions
Doesn't seem like that's going to cause much issue for any legitimate client from the past 10-20 years. He only recommends blocking HTTP 0.9/1.0, which fair enough
Append a #hash to the form’s action URL
Hah. Clever man. I don't see how this is going to stop any legitimate user from loading your website or submitting the form, but I can see how it might frustrate bots.
Include a hidden prefilled form field
This is just standard practice to mitigate CSRF.
Verify the Host and Origin request headers
Yes. You should be doing that.
Set a test cookie and verify it gets included in the submission
Another CSRF trick.
Swap the name attributes in the name and email fields
This one's a little user hostile to folks who use assistive devices like screen readers. But still won't prevent you from accessing the site in the first place.
Verify the POST/Redirect/GET (PRG) chain
As noted by the author, might cause some issues but again, won't stop anyone from loading your website.
Block ancient versions of common browsers
Alright please just don't do this. UA blocking is gross and might prevent access through specialist software. But he also calls this out himself.
I strongly discourage you from blocking or discriminating against unknown or uncommon browser User-Agent request headers
All in all, with the exception of UA blocking I don't see how any of these mitigations would result in users not being able to access said website, or having their loading times drastically increased.