Doing a 1 line command that checks for multiple entities (by chaining "as") does not work in command blocks. It does however work when it's done in chat.

The command I used was

/execute as @e[type=item,nbt={Item:{id:"minecraft:flint"}}] as @e[type=item,nbt={Item:{id:"minecraft:feather"}}] as @e[type=item,nbt={Item:{id:"minecraft:stick"}}] run say "Propagated between Flint, Feather, and Stick"

Video is here
https://youtu.be/PRT8NMhGawo

Edit: Despite the video showing a conditional command block (which is default, by the way), it doesn't work with an unconditional block either