Would the object be implicitly required if it has some required properties?

---

Would this object be implicitly required?

---

No.

To make this object required you'll need to include it in the "required" list of the parent object:

A:
  type: object
  required: [b]    # <----------
  properties:
    b:
      $ref: '#/components/schemas/B'

B:
  type: object
  required: [foo, bar]
  properties:
    ...