The article doesn't really explain why you might want to use client mode (other than use as a WiFi adapter for some equipment) which could lead someone to think this is necessary for AirPlay 2 targets. It might be good to add a sentence to one of the first few paragraphs of the article to explain that. Simultaneous dual-band 802.11ac wireless Gigabit Ethernet WAN port for connecting a DSL modem, cable modem, or Ethernet network USB 2 port for connecting a USB printer or hard.
In these cases, client mode would likely fix the issue as you mentioned. AirPort Utility for Mac available for free download AirPort Utility for iOS available for free download Bonjour for Windows available for free download Interfaces. You are right that if a person tries to extend the network of another router, it sometimes just doesn't work reliably. If the Express is connected to the other router via Ethernet back-haul it should also work fine. You can also share files among computers. Looking at eBay already, there are a lot of people looking to get the Express all of a sudden. the Internet and share the connection with computers and other wireless devices, such as iPad, iPhone, and Apple TV. If youre using a DSL or cable modem, make sure its connected to the telephone or cable jack and to the base stations wide area network (WAN) port. But, it works better with other manufacturer's routers if you do so. As-is on an AirPort-centric network, it works fine. Just keep in mind that it is not necessary to set up an AirPort Express in client mode to use it as an AiprPlay target (and by extention, any seperately sound system that is connected via audio in).