Managed package code is always expanded in Solution Exporer after being pulled from the source Org. This was fixed for Unmanaged code a long time ago, but appears to have been missed for Managed Package code
Managed Packages - Solution Explorer shows everything expanded after pulling
Posted 08 May 2018
Thank you for contacting us on this.
A reason for this behavior is the same that I've described in this topic - since the IDE tracks a whole package as one element all the operations on this package are applied to the included files.
This is why TWS expands these files in the Solution Explorer as updated ones after pulling. The same applies to regular files from an organization, unmanaged code - updated or added files are expanded after the pull from Salesforce.
We will consider what we can do to make this process more convenient.
The Welkin Suite