You were told correct, it has been known for many Oscars to take a disliking to plants. My two large Oscars used uproot them all the time. Having said that, I don't see why every Oscar should uproot plants, some people do claim to keep plants and Oscars together okay. If you want some plants, I would put him in now whilst the Oscars are still small. Make sure you put the plants in really well so that the roots take hold. I am afraid I'm not an expert on plants so I can't really give you many names. The most successful than I have kept with Oscars was a very long reed type plant. I got these plants when I got the Oscars and it put down a fantastic root system which they just could not budge. The only problem I might have is if your tank is in darkness quite a lot. I have found that plants do well when there's lots of light, problem is, you shouldn't really keep the lights on for too long. . Unfortunately, it can be a bit hit and miss keeping plants healthy. If you are serious about plants, you may want to consider getting plant food, this may help them growMake sure you get proper plant food for aquariums. I did try, but it was too expensive for my size tank.
So, if you want plants, try and choose ones that are quite tough, don't bother with ones that break up easily, the Oscars will just rip them to pieces in no time at all, even if the roots don't come up. Java fern and Java Moss are quite tough. I did have some but they didn't fare too well because I don't think they got enough light.