Hi MicroDex,
Regarding your concern about if this is an expected behavior, sorry but I can not confirm as after much research I didn't find and official documentation stating this.
>> Any links were we can find mitigation to disable the same without having to remove the Security patch.
Based on my test, we may try the following steps to remove the Store Add-in button:
1. Go to File > Options > Customize Ribbon.
2. Select Add-ins, click Remove, click OK:

Hope this can be helpful.
Best regards,
Yuki Sun
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