Is there any significant difference between using SELECT ... FROM ... INTO syntax instead of the standard SELECT ... INTO ... FROM?

I was creating a function following an example from a database class which included the creation of a temporary variable (base_salary) and using a SELECT INTO to calculate its value later. However, I did not realize I used a different order for the syntax (SELECT ... FROM ... INTO base_salary) and the function could be used later without any visible issues (values worked as expected). Is there any difference in using "SELECT ... FROM ... INTO" syntax order? I tried looking about it in the PostgreSQL documentation but found nothing about it. Google search did not provide any meaningful information neither. Only thing I found related to it was from MySQL documentation, which only mentioned about supporting the different order in an older version.

There is no difference. From the docs of pl/pgsql:

The INTO clause can appear almost anywhere in the SQL command. Customarily it is written either just before or just after the list of select_expressions in a SELECT command, or at the end of the command for other command types. It is recommended that you follow this convention in case the PL/pgSQL parser becomes stricter in future versions.

Notice that in (non-procedural) SQL, there is also a SELECT INTO command which works like CREATE TABLE AS, in this version the INTO must come right after the SELECT clause.