magento2: Depending from multiselect in backend is broken

Preconditions (*)

1. Magento ^2.2 (and probably earlier)

Steps to reproduce (*)

1. Create a module with an etc/adminhtml/system.xml file

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <section id="general">
            <group id="test" showInStore="1" showInWebsite="1" showInDefault="1" type="text" sortOrder="999">
                <label>Proof of concept</label>
                <field id="multiselect_id" translate="label" type="multiselect" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="0" canRestore="1">
                    <label>multiselect_id</label>
                    <source_model>Magento\Sales\Model\Config\Source\Order\Status</source_model>
                </field>
                <field id="brand_attribute" type="text" sortOrder="3" showInStore="1" showInWebsite="1" showInDefault="1" translate="label,comment">
                    <label>Brand attribute</label>
                    <depends>
                        <field id="multiselect_id" separator=",">processing</field>
                    </depends>
                </field>
            </group>
        </section>
    </system>
</config>

1. Select all the options

Expected result (*)

1. The depending field should appear and become editable

Actual result (*)

1. The field remains hidden until one unselects all options preceding the one one depends from

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Please provide Severity assessment for the Issue as Reporter. This information will help during Confirmation and Issue triage processes.

• Severity: S0 - Affects critical data or functionality and leaves users without workaround.
• Severity: S1 - Affects critical data or functionality and forces users to employ a workaround.
• Severity: S2 - Affects non-critical data or functionality and forces users to employ a workaround.
• Severity: S3 - Affects non-critical data or functionality and does not force users to employ a workaround.
• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.