In my opinion, it was very necessary. I didn't see is as immature, but saw it as a shot across the bow of those few people that frequently show up around here with "white knight syndrome". I laughed a lot, and didn't mind it taking me out of the mood of the game for a few moments. Plus, whenever we see one of these folks show up, we can just shout "Filius, it is you!".
The sense of infantile entitlement of a vocal few of the commenters in this thread over the years has been unbelievable. If a player doesn't like the game, fine, either keep it to yourself or maybe offer constructive criticism if you feel you have something new to say, but to constantly harp on the fact that Hopes is focusing on developing a believable story, and that the game is ruined and pointless to play unless Hopes makes the MC jump in bed with the daughters of the don after just a few weeks, is very childish and completely unrealistic to the story and its characters. Even with a kiss, he takes his life in his hands. And Luna and Gracie are not the typical oversexed females present in most of the VNs here. No matter how pleasant and decent looking the MC is, in a story approximating real life characters, in a dramatic situation, neither Gracie or Luna are likely to want to sleep with the MC after just a short time. It would be very jarring to the story if one day it just happened. I applaud Hopes for sticking to his guns and telling the story he wants to tell, rather than caving to a few vocal complainers like some devs do.
And Hopes makes an important point in that these people aren't just happy just to complain once and then go play something else that is more to their preference, but they have to spend hours playing each update, just so they can come back to the forum here and complain some more. And the "white-night" attitude is especially misguided. They seem to feel like they are doing other players a huge favor (or pretending to), by pointing out over and over again what is obvious on the first page of the thread, and pretty much everywhere else.
Anyway, I don't really feel the need to see Filius show up in the game again, but I think it was a humorous way for Hopes to make his point, and since the complainers secretly love Deluca Family and are first in line to play each update so they can have a new round of complaints ready, I am sure they all saw the satirical depiction of themselves. I wonder if they all looked up what Filius Canis means in Latin.