bluehost.in and bluehost.com are different. The author of your article says in the comments:
The Indian branch at bluehost.in doesn’t support free SSL unfortunately. And neither have they wanted to comment on any plans to implement it in the future.
Not sure if that’s outdated, or if he was specifically referring to “WordPress Hosting”. bluehost.in does do free SSL now, but with cPanel and Plesk only:
(You can probably log in and see the original at https://manage.bluehost.in/kb/answer/2964 but I can’t.)
They could have overridden cPanel AutoSSL’s default Comodo/CPanel CA to use Let’s Encrypt, but they don’t say. Plesk uses Let’s Encrypt of course.
Their “WordPress Hosting” doesn’t seem to support automatic free SSL, though. It appears bluehost.com uses a streamlined CPanel for that, while bluehost.in uses something else that doesn’t support it. They also have a “Legacy Hosting” product that probably doesn’t support it either. Note that “WordPress Hosting” is a different thing from just running WordPress on regular Web Hosting.
Basically, if you can find the things to click on in their help article, click on them! If they give you an error, let us know what error you get and we can try and help you. If you don’t see those things to click on at all then your plan probably doesn’t support automatic free SSL, sorry.