We don't know the true answers to your questions. As with anything, we can only speculate. Just because the whole world knows that MJ is supposedly buried at FL, that doesn't mean that FL has to acknowledge it on their website etc. They have policies that were in place long before the alleged burial of MJ in September, so they aren't doing anything for "MJ" that is unique to just him.
As for TMZ, they are not the Gospel. Many people believe MJ owns TMZ or they're in it together. I do not. But either way, what TMZ says is not the last word of fact on Michael Jackson, his alleged burial, or anything else. They also could have been referencing Forest Lawn in the Hollywood Hills, where the "body" was in July. It wasn't buried there. It was buried at Forest Lawn in Glendale.
There are numerous accounts of a private family memorial service (not a burial) before the Memorial. You can find them all over the Web with a simple Google search. It was just a memorial service. But again, that service would have taken place at Forest Lawn in the Hollywood Hills, not Forest Lawn in Glendale, where the funeral service was held in September.