The biggest caveat between the mount boxes and regular BLCs is that you can easily farm keys by doing map exploration and your weekly lvl 10 story it's reasonable enough to get 4-6 keys a month and put those toward opening chests, but with the mounts, you're forced to use gemstore conversion rates at a much steeper cost if you don't want to gamble. It's like they went one step in opposite directions for the mount boxes: one forward with having them separate from the nightmare that is BLCs with no dupes, and one back for forcing all those skins to be RNG instead of being allowed to buy what you want.