Luka really did tell Marinette's parents the long and short of the situation - minus certain details pertaining to the identities of the other holders, to ensure they would continue to act natural around Alya and her previous friend group whilst pretending that Marinette is "missing."
In spite of how he monopolizes Marinette for her "safety," he really does hope that soon, he can reunite them. Having her parents back would do wonders for Mari's mental health, but for the time being, the bakery could be under some pretty harsh surveillance from Chrysalis, so Luka only dares a visit on special occasions.
Marinette doesn't recognize her parents, but, she finds herself intensely comfortable at the bakery, and wonders why Luka won't let them drop by more often, given how regularly she talks about how much she likes the food...