I believe you get more points depending on a couple of other factors. One, how much of the map your wards covered. You'll see that top laners tend to get lower scores and junglers tend to get higher scores and this is because top is mostly warding just their area (worth less vision score) while the jungler is warding all over the map (worth more vision score) and often warding in the enemy jungle (worth even more).
Two, what your wards and vision saw. If you place a ward, and it dies without anyone every walking over it, that's worth less than a ward that sees a lot in a high traffic area. So if all other things are equal between supports, but the enemy support is better at predicting where the enemy will be next and warding accordingly, they will get more points.
Third, abilities that reveal vision will contribute to your vision score. Teemo's shrooms contribute to vision score, moreso when someone steps on them from fog of war. Ashe tends to get decent vision scores for an ADC because of her Hawkshot. So if the enemy support had something that reveal the enemy, this would contribute to their vision score. Although, considering you were Lux, you'd think you would have crushed in this category, seeing as your E grants vision. Lulu's E on enemies is another example.
Lastly, if your ward lasts the full 3 minutes, you get more points than if it was killed shortly after placing it. Same goes for killing wards: you get the most points from killing a ward if you kill it while it has a long duration left.
This is my analysis as I understand it given what Riot has told us. Good warding and better luck next time!
I also found this from Riot: https://boards.na.leagueoflegends.com/en/c/developer-corner/4Pv0FcII-vision-score-details