magento2: Inconsistent location for plugins

I have noticed in app/code/Magento/CatalogUrlRewrite the location where Plugins are kept is inconsistent between Blocks & Models.

So in the code below (from app/code/Magento/CatalogUrlRewrite/etc/adminhtml/di.xml) shows Plugins for Models stored in the Model directory, but then Blocks and Controller Plugins are kept in a Plugins directory within the root of the module.

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    ...
    <type name="Magento\UrlRewrite\Model\StorageInterface">
        <plugin name="storage_plugin" type="Magento\CatalogUrlRewrite\Model\Category\Plugin\Storage"/>
    </type>
    <type name="Magento\Catalog\Block\Adminhtml\Category\Tab\Attributes">
        <plugin name="category_form_url_key_plugin" type="Magento\CatalogUrlRewrite\Plugin\Catalog\Block\Adminhtml\Category\Tab\Attributes"/>
    </type>
    ...
    <type name="Magento\Catalog\Controller\Adminhtml\Product\Initialization\Helper">
        <plugin name="product_save_rewrites_history_plugin" type="Magento\CatalogUrlRewrite\Plugin\Catalog\Controller\Adminhtml\Product\Initialization\Helper"/>
    </type>
</config>

Is there a reason behind this? Was it intentional?