Jason commented on Bold Apps Product Options items in cart grouped - Shopify items in Checkout Ungrouped

This has nothing to do with the templates. The app gives the illusion of a single product but once you hit checkout Shopify will show them as they truly are - individuals. If you must 100% show them as one item in the checkout you'd need to rethink how you're putting your products together.

You could create a single item with 4 variants:

1. strap
2. strap + lock
3. strap + custom colour
4. strap + custom colour + lock

Picking the colour would be done with line items.

Another similar example you could make four separate products .

1. strap
2. strap + lock
3. strap + custom colour
4. strap + custom colour + lock

Harder to manage stock with those approaches however as each strap will be independent of each other. 

A custom app could also dynamically create a product with the price and options you need but that's generally more development costs than most need.