RFC 2182 details the operation and functionality of secondary DNS servers. Which defines/influences how resolvers behave with multiple DNS servers.

When you specify more than one DNS server for network clients, the order in which these servers are used is not random. The following sequence is observed:

Primary DNS Server: Clients will first attempt to use the primary DNS server specified in their network settings. This server is often considered the default.

Secondary DNS Server: If the primary DNS server is unavailable or unable to resolve a query, clients will then attempt to use the secondary DNS server. This server acts as a backup.

So in OPs case his Pihole will always be used if it’s available, and only when it’s not will the secondary be used.

Microsoft has openly encouraged piracy as far back as the 90s. I remember an interview with Gates where he said as much.

This has been part of Microsoft’s business model, especially for Windows and Office for 30 years. They actively encouraged pirating the software to ensure it cemented itself as the defacto standard in homes and offices with a view that one day users would have no choice but pay for it. For over 20 years now this has been part of the bigger desktop-as-a-service goal.

Soon businesses and home users will have no choice but to remotely log into a Windows system that is hosted in a datacentre and provided by Microsoft or one of their partners. Local installs will be a thing of the past. Think Citrix Presentation Server and thin clients which is where this whole idea started a long time ago.