You can add Surpass Hosting to the list of companies with "No Planned Support".
You are correct, as of cPanel/WHM 58 Let's Encrypt has been officially supported by cPanel as an add-on for their AutoSSL feature:
Unfortunately, at this time we do not have any plans to officially support Let's Encrypt on our shared and reseller servers.
If Let's Encrypt is something you are interested in using, we would recommend upgrading to one of our VPS or Dedicated Server plans. Both would offer a huge upgrade in the freedom for your hosting environment, and the add-ons that can be installed on it. (Including Let's Encrypt)
Support Technician I
I found their response quite infuriating because in my original request I kindly explained that I am using Surpass to host a couple of very small personal domains that get maybe 20-30 hits per month as per Google Analytics, and so SSL isn't something I really want to pay extra for if it can be avoided.
And yet, this support technician is suggesting that I start shelling out $75+ a month for this.
Time to start looking for a new host, I guess.