A wandering merchant cannot be named with a tag.
When you try to give the merchant a name, the trade window opens. There is no such bug in the Java version. There you can give a name to a traveling merchant.
The problem is also present on android devices.

Summary:
In the Bedrock version, it is not possible to name the itinerant trader with a tag, although it is possible in the Java version!

Steps to Reproduce:

1. Name the tag using an anvil.
2. Wait for the wandering merchant to appear or summon one.
3. Try giving a name to a traveling merchant.

Observed Results:
A trading window will open.

Expected Results:
The merchant will receive a name (as in the Java version).