There is no issue as you mentioned, I've checked on M2.4.2.
In order to get specific store order data try using below api
You can check quote items count after LoginPost action.
The di.xml (preferably frontend/di.xml since you only need to do the redirect on front) code:
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
It's very old question, but sadly noone answered it. I bet the author has more knowledge now, so he could answer it himself now :)
Nevertheless, your question was theoretical, so I won't provide the code with working functionality, but rather use my experience with Magento 2 backend developer to put you in the right direction.
Why core functionality ...