Does a narrator practice Tadlis upon a specific sheikh without doing so upon another, and is Ibrahim al-Taymi a Mudallis as al-Karabisi stated, and does he practice Tadlis upon everyone he narrated from?

Some narrators practice tadlis (concealment) from a specific شيخ (teacher/elder) or more. Among them are Abu Nu'aim Al-Asfahani and Ayyub Al-Sakhtiyani. Another is Ibrahim bin Yazid Al-Taymi, who narrated from his father and reported from Aisha, Ali, Ibn Abbas, and Anas, even though he did not hear directly from them. Al-Karabisi affirmed that most of his narrations from Zayd bin Wahb were Mudalasah (concealed).