The thing that makes the above two introduction letter examples different from what you will typically find online is that they are "real-life templates". In other words, they are complete, fully-formatted letters, written by professionals for actual real-life business situations.
These are NOT your typical fill-in-the-blanks templates. They are complete letters that one can quickly learn from and adapt to fit one's own situation.
When you need to write a letter of introduction or introduction letter, it is always helpful to have some real-life samples that show you exactly how a professional writes a letter for a similar real-world situation.