A route in al-Bukhārī may be represented as “al-Bukhārī ← Qutaybah ← Mālik.” Imagine that a later transmitter has eight intermediaries to Qutaybah by way of al-Bukhārī, but reaches the very same Qutaybah through an independent route involving Abū al-ʿAbbās al-Sarrāj with seven.
Qutaybah is the common meeting point. The second route reaches him without passing through al-Bukhārī, so it is muwāfaqah; with one fewer link it also offers relative elevation at that point.
The relationship is not that the later researcher becomes al-Bukhārī's student. The test is whether the same hadith reaches al-Bukhārī's teacher by another route.