Using more than one `execute anchored` per command doesn't work as expected and only the first one is applied.

Examples to reproduce (put them in a repeating commandblock):

execute as @a at @s anchored eyes run particle minecraft:basic_flame_particle ^^^3

will put the particle 3 blocks in front of where the player is looking.

execute as @a at @s anchored feet run particle minecraft:basic_flame_particle ^^^3

will put the particle 3 blocks in front of where the player is looking, but forward based on the feet position.

execute as @a at @s anchored eyes anchored feet run particle minecraft:basic_flame_particle ^^^3

will put the particle 3 blocks in front of where the player is looking, instead of at the feet.

execute as @a at @s anchored feet anchored eyes run particle minecraft:basic_flame_particle ^^^3

will put the particle 3 blocks in front of where the player is looking based on the feet instead of the eyes.

You might say "but why would you want to do that anyways": in more complex execute commands, being able to switch back and forth between these is very helpful.

For example, using the method described here you can use a single execute command to check whether a player is roughly looking in the direction of something.