No - individual products do not need to be available as standalone items to feature as part of a bundle. Products can be excluded from your sales channels via their respective Product pages and still appear in your bundles.

This is possible because Bundle Builder doesn't check if there's an active sales channel for individual products. This makes it simple to include products inside your bundles that are otherwise not for sale on your site.

To make a product unavailable from the rest of your store while keeping it as a component of a bundle:

Step 1: Go to Products within your Shopify admin space and select the product you want to make unavailable.

Step 2: Locate the Publishing section (containing Sales channels) and click Manage.

Step 3: Proceed to Manage sales channels.

Step 4: Disable Online Store availability. This will leave the product available for Bundle Builder to use, but will no longer appear in your collections or search results.

Step 5: Save your changes.