Specter shows two Zpubs and one Xpub despite SLIP132 turned on

**Describe the bug**
Specter isn't showing Zpubs for all 3 of my multisig keys. Only for 2 of them

**To Reproduce**
Steps to reproduce the behavior:
1. Click on your multisig wallet in the left pane
2. Click the Settings tab
3. Scroll down on Wallet Info and click on "Show key details"
4. Toggle the SLIP132 button
5. My Coldcard (1st key) and Paper wallet (3rd key) will change from Xpubs to Zpubs. But my Keystone wallet (2nd key) will remain as Xpub

Alternatively
3. Click on "Export" tab
4. Scroll down to "Printable PDF Backup"
5. Export the file with the SLIP132 toggle on, and the pdf will still not show Zpub for my Keystone wallet

**Expected behavior**
All 3 master public keys should be Zpubs in both locations

Reproduce the issue from the Settings > Wallet Info > Show key details path and from Export > Printable PDF Backup with SLIP132 enabled. Compare the three multisig keys, especially the Keystone key, with the Coldcard and Paper wallet keys. Done means all three master public keys appear as Zpubs in both locations.

Written by the indexing model from the issue text.