These commands need to be added to package.json's contributes/menus/commandPalette section with:

{
    "command": "mssql.launchDacpacDialog",
    "when": "mssql.enableExperimentalFeatures"
},

As is, these still show up in the command palette, but error out because the flag being off means they aren't actually registered.

Originally posted by @Benjin in #20505 (comment)