Is it necessary to import jquery in Ember CLI 1.13

I am working on an old project which uses Ember CLI 1.13.12 where every file (including app.js/controllers/routes/components) has the following import at the top

import $ from 'jquery';

I removed the above line from all the files and still the app is running perfectly with all jquery code ( using $() or this.$()).

I tried to find if jquery is enabled in any config file but I couldn't. Also, there is no optional-features.json file in the project where jquery-integration can be set to true.

So, is it necessary to import jquery in an Ember CLI 1.13 project?

Can we disable the default jquery in Ember CLI 1.13?

I am new to Ember and that too to an old version so finding it difficult to understand.