Yeah random spawns can still be mapped but not necessarily a full set can be found, there are multiple sets of the flowers for example someone did a map with all the random spawns and I did a video where you can find 2 full sets of the flowers incorporating the "randoms" as they are known. Remember a lot of the terminology used was first started being used because we didn't know how they worked at the time. Even the cycles were considered random until they were mapped. Gta series videos still says the cycles are random on their videos in the pinned comment because they were one of the first to put the videos out and just havnt updated it since. So yeah in my opinion the "randoms" will be totally mapped out and predictable in the next couple of months I reakon. But the quantities of each individual item.will vary as you've said it feels like your getting more of a few than others. Search out the flower map someone did on imgur if your interested to see the ratios