There are a bunch of slot suggestions starting with weapon.* that aren't meaningful, and which aren't documented in the 24w10 article. For example weapon.*0 corresponds with weapon.mainhand and weapon.*3 corresponds with armor.legs.

How to reproduce:

1. Type the following command in chat, and notice the suggestions

   /execute if items entity @s weapon.*
   

2. Run the following command, and notice that the item is placed in your legs slot

   /item replace entity @s weapon.*3 with minecraft:chainmail_leggings