You do not need to put the methods in the "model.js" file, you can put them anywhere, they just called the model.js file in the video.
Meteor.methods is the Anywhere method, which means that it can exist both on the server and on the client. If you look at the documents , you will see the explained difference:
Call methods on the server define functions that clients can call remotely.
[...]
Call methods on the client define stub functions associated with server methods of the same name.
In the video, they show you a demonstration of how the methods and other functions of Meteor work, so they were not related to the specific placement of methods on the server.
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