[Bug report] Unexpected change with isPlainObject

[Mister-Hope]

Description

The above image should show the main difference of the previous one and the new one.

The new one is losing the ability to type cast to a specific interface

[Mister-Hope]

The isPlainObject also has some fail positive comparing with typeof x === 'object':

interface Test {
 key: string
}

let test: Test | false;

if (typeof test === 'object') {
  // test is now Test
}

if (isPlainObject(test)) {
  // oops, test is now Record<string, unknown>
}