I too have noticed this. Is that what causes the error when trying to run with yarn develop after the steps you mentioned above? (Fresh plugin generated with Typescript, install node_modules for plugins, build and then run.
ERROR in ./src/plugins/test/admin/src/pages/App/index.tsx:17:8
TS2786: 'Switch' cannot be used as a JSX component.
Its type 'typeof Switch' is not a valid JSX element type.
Type 'typeof Switch' is not assignable to type 'new (props: any, deprecatedLegacyContext?: any) => Component<any, any, any>'.
Construct signature return types 'Switch' and 'Component<any, any, any>' are incompatible.
The types returned by 'render()' are incompatible between these types.
Type 'React.ReactNode' is not assignable to type 'import("/home/harvey/Projects/strapi-ts/node_modules/@types/react/index").ReactNode'.
Type '{}' is not assignable to type 'ReactNode'.
15 | return (
16 | <div>
> 17 | <Switch>
| ^^^^^^
18 | <Route path={`/plugins/${pluginId}`} component={HomePage} exact />
19 | <Route component={AnErrorOccurred} />
20 | </Switch>