Magento 2 single store mode still exports products for both store views?

Question

Why is a magento 2 site in single store mode still exporting products from global and store view stores?

These products were initially migrated using the data-migration-tool from magento 1

Answer 1

This is normal behavior.
Single store mode can be enabled if you only have 1 store view.
And this is a way to remove some store selection fields from different admin screens.
If you have 2 or more store views, the setting "single store mode" is ignored.
The result of the single store mode is determined in Magento\Store\Model\StoreManager::isSingleStoreMode.
the method looks like this:

public function isSingleStoreMode()
{
    return $this->isSingleStoreModeEnabled() && $this->hasSingleStore();
}

where isSingleStoreModeEnabled checks the config setting and hasSingleStore checks count($this->getStores(true)) < 3.

Why 3?
Because the admin is considered a store. So this only works if you have one frontend store view and one admin store view.
summing up, in your case isSingleStoreMode will return true & false which evaluates to false.