I must have not been clear. URL shorteners like bit.ly and goo.gl are safe to use on YouTube as the link will go directly to the intended site. URL shorteners like adf.ly are not allowed as those go to a middleman ad page first before directing.
Example: You made a video about, in OP's case, video templates and you wanted to include a download link. The service you are using gives huge URLs that are crazy long so you want to use a short URL to redirect to the download link. In the video, you mention there is a download link in the description that viewers can access.
Here is where the differences come into play:
- You use a bit.ly/goo.gl link to download. YouTube is okay with these as the link goes directly to the download page.
- You use a adf.ly link to download. This is not okay as the link goes to a page of ads before going to the download page.
Use of redirection URLs that go somewhere other than the original destination is considered deceptive (and violates the TOS).