Apple Music plays content that’s not downloaded when offline

iPhone in Airplane mode / No Wi-Fi / No Cellular plays music content that’s not downloaded.

# Airplane mode / Not connected to Wi-Fi / Cellular

# Play music on shuffle

# Plays a song

# Click on GO TO ALBUM….All songs are greyed out as though not downloaded

# Select the song that is currently playing and receive info’ message…“connect to wifi or mobile network to play music” 

# Search for the song in DOWNLOADED - no result

What is going on? How can it play songs that are supposedly not downloaded when offline? 

This happens with dozens of songs.