The issue is with the list method signature (which is actually correct in the docblock above it).
NAMESPACE.list({prefix?: string, limit?: number, cursor?: string})

If I call the list method like this:
KVNAMESPACE.list('my_prefix').then((mylist) => {...
then it compiles but during execution it thorows the following error:
TypeError: Failed to execute 'list' on 'KvNamespace': parameter 1 is not of type 'ListOptions'.

If I call the list method like this:
KVNAMESPACE.list({prefix: 'my_prefix'}).then((mylist) => {...
then my code won't compile becasue I get:
Error:(35, 25) TS2345: Argument of type '{ prefix: string; }' is not assignable to parameter of type 'string'.

only if i do:

// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-ignore
KVNAMESPACE.list({ prefix: prefix }).then((mylist) => {...

then it will run.