At that point, none of the canonical gospels were considered "scripture", and a reader/hearer could feel that some facts in them could be wrong, that is, if s/he were even aware of this fact.
Consequently, the lack of the husband's name in gLuke does not prove borrowing from Josephus' Antiquities, but only that s/he may have thought the name was different than the Philip of Mark/Matthew. Alternately, the author of gLuke could have been aware of traditions in which the husband of this Herodias had a different name.
All we can say for sure is that s/he just wasn't sure it was Philip.
Sure, one can make many assumptions...
So - the writer/writers of gLuke decided that the authors of gMark and gMatthew had got their Herodian history wrong in regard to a husband of Herodias? gMark and gMatthew telling their Herodias and Philip marriage story for x number of years without anyone throwing the history book at them? Only with the arrival of Antiquities, around 93/94 c.e., could the Herodian history of gMark and gMatthew be questioned. Or, contrary, of course, the Herodian history of Josephus could be questioned...
Actually, the far more interesting question is not why did gLuke drop the mention of Philip being a husband of Herodias - but why did Josephus write that it was a daughter of Herodias that was married to Philip?
Nikos Kokkinos has questioned the Herodian history given by Josephus in Antiquities. Kokkinos gives Herodias three marriages. Herod III, Philip and Antipas. Thereby rejecting the Antiquities story about the daughter of Herodias, Salome, being married to Philip.
- Nikos Kokkinos: The Herodian Dynasty.
The stubborn insistence of many theologians on referring to Herod III as 'Herod-Philip' is without any value. No such person existed - he is an illusion created to account for an apparent contradiction between the Synoptic Gospels and Josephus. The reference to 'Philip' in Mark, Matthew and Luke is inevitably to Philip the Tetrarch. (page 223).
According to Ant.18.137, Philip married Salome III. But this does not seem to be right. For him to able do that he should have stayed celibate up to the age of at least 40 - uniquely among the Herods. (Salome could not have married before c. CE 13). From other evidence we may actually deduce that Philip's wife (during the first three decades of the Christian Era) was Salome III's mother, Herodias I, who had divorced her first husband, Herod III, and later also resorted to marrying Antipas after the death of Philip. (page 237).
The facts as we have them still stand. gMark and gMatthew have Herodias married to Philip - as does material in Slavonic Josephus. Antiquities tells a different story about Herodias. gLuke chose to drop the mention of Philip in connection to Herodias. Thus allowing Antiquities to influence his 'update' of the gMark and gMatthew Herodias and Philip story: Failure to name the brother from whom Herod Antipas took Herodias....Prior to Antiquities there would be no reason for the writer/writers of gLuke to fail to follow gMark and gMatthew in their Herodian history.
Tread softly because you tread on my dreams.