CXX is right in the fact that we don't know
definitively that it will constitute a harem, but many of us expect the game to follow in the footsteps of the dev's prior game
F.I.L.F. which culminated in
a large family fuck-fest at the end. In other words, you were basically fucking every single LI available in the game and they were all cool with it. That game also had the harem tag, btw.
Non-harem games generally have choices that put you either on or off the path of particular LI's. Thus far, there are no choices you can make in this game that prevent you from enjoying any content with any other LI. In other words, you are free to romance them all.
A major difference in this game from F.I.L.F. is that your mom (Julia) is married to Penny. Since they are already in a relationship of their own and therefore sexually involved with each other outside of anything involving the MC,
SOME PEOPLE on this forum would argue that it violates the proper definition of a harem. Personally, I disagree and I quite frankly enjoy it when the women also fuck one another.
More to the point: If you are fucking all the women and if they are all essentially okay with that fact, its a harem game. Period.