Oxygen mask for infant on on right side of A330?

My family (2 children, 2 adults) has been separated by the anonymous computer "system" despite us booking seats together months ago. The agent at Delta claimed that since I am holding an infant I must sit on the right side of the plane. Is that true?
Apparently their "system" only caught this problem two months after I booked the seats. Does this sound credible? I feel they needed two seats together and so they bumped me to another seat (my husband and I do not have the same last names and for a variety of reasons our confirmations were not on the same record). Nowhere in manuals for airbus did I read that the extra oxygen masks are only on the right side.
Can someone shed light on this before I send a nasty letter to corporate?
Thanks so much

Not sure about the Airbus, but on the CRJ's it's true. Infant O2 masks are on the right side. So I can only assume its true for an Airbus. Otherwise the flight attendant would have to move you as well?

Edit to add:
Thought your post said 320 instead of 330. But it still could be true.

Thanks! I had read that about the CRJs as well but had read elsewhere that Airbus has one extra mask per row (did not say where). Well, I guess I am just quite cynical as I read a research paper a while ago that documented how airline personnel often lie about issues to get passangers off their backs. But perhaps that is no longer true. I can certainly see how in these hard flying times one needs to resort to all kinds of tactics just to get through the day.

Not sure how the lying comes into play with this but we often had to move passengers with lap babies because of oxygen masks. I doubt an employee would come up with a story like that just to get a passenger "off their backs".

Globally, there was an extra mask for three seats and two extras in blocks of 4 or 5 seats in one row. Basically, we tried to keep parents with lap twins in the center section. We had Airbuses but remember almost all my flying was long haul international on the bigger aircraft. I don't know the smaller planes you find on domestic flights. What kind of Airbus is this? If there are two seats on the left side and three on the right, that would make sense. Never seen it but it could be possible.

The Oxygen mask information is not that easy to find. It was in our manuals. Glad though that they have it in the reservation system since many parents found out the hard way and it could be very difficult to reseat them during boarding!

the A330 is a widebody, for delta both the A330-200 and the A330-300 show a 2-4-2 layout

I know on the BA airbus (narrow bodies) that the spare masks alternate, but it's different between the various aircraft types as well.

The seatmaps can account for this so when you go to assign a seat with an infant you get lots of seats blocked out (like every other row) whereas this isn't the case if you select someone without an infant attached to the booking.

Thing is, if they change the aircraft (say from an A321 to an A320), 8DEF as an example no longer has a spare O2 mask and you get reassigned!