[Bug Report][4.1.0-beta.0] VExpansionPanels no longer rounded by default since 4.1.0-beta.0 #23229

Environment

Vuetify Version: 4.1.0-beta.0
Vue Version: 3.5.43
OS: Linux undefined (current)

Steps to reproduce

1. Open the reproduction link with Vuetify 4.0.9: the panels are rounded.
2. Switch the playground to 4.1.0-beta.0 (or 4.2.2): the panels have square corners.
3. Inspect the .v-expansion-panels element: it has the rounded-0 class.

Expected Behavior

Without the rounded prop, the panels are rounded (border-radius: 4px from the component CSS), as in Vuetify 3 and up to 4.0.9

Actual Behavior

Without the rounded prop, the root element gets the rounded-0 class and the panels have square corners.

Reproduction Link

https://play.vuetifyjs.com/#...

Other comments

Since 4.1.0-beta.0, VExpansionPanels declares rounded: [Boolean, Number, String, Array] without default: undefined (4.0.x used makeRoundedProps(), which has default: undefined). Because the prop accepts Boolean, Vue casts the missing prop to false, and useRounded(false) adds rounded-0. Adding default: undefined should fix it. Still present in 4.2.2.