Shapers VS builders. How do shapers keep connected to the engineering side of things?

One thing I am very clear about in ShapeUp is on how separated Shapers are from Builders (in the teams large enough to have them specialized as the guide recommends).

If the most senior engineers work mostly (or completely?) off cycle on shaping projects then doesn’t it create much of the disconnection between these groups of people? How do Shapers keep up to date with what happens in the code, how is the communication with Builders happening? Does it create a disconnection between “really cool people who decide on things” and “just builders”? Do Shapers do just shaping and after the betting table just hand it over to Builders in your team?

An example to make it live
For example the top management got an idea of some great new way engine to make reports for the customers, maybe even customizable for the customers.

When shaping some principal engineer(s) with a product manager can sketch what it could look like, research some engines/libraries to base on. If it’s first time we are doing something like this, engineer would probably do a proof of concept to verify that library is up to the task and which reports can/cannot be done with it easily (patching the rabbit hole).

Then if it wins in the betting table it goes passed to Builders and… what do the Shapers do? Just move to the next proof of concept for the next bet? Help the implementations with the advice? Do they communicate with builders much at all?