Real value will suffice, as per an earlier case concerning Runescape effort and time spent can be considered comparable to monetary value.
Thus anything affecting skill or time spent can be considered as having real value, thus being sufficient to deem it gambling.
There is a reason they have not risked it, they know they would very likely lose; their lawyers aren't fools. So stating that it has been, effectively, denied is not inaccurate; the law works as intended in scaring off abusive market participants.
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No, value is definitely a question of law as far as digital goods are concerned, there have been several cases on this. The one that comes to mind is whether digital theft in Runescape is actually theft, since nothing material is taken.
In that case it was determined that digital goods can be considered to have value if significant effort (time, skill, etc.) had to be spent to obtain it.
P2W is indeed an easier case, but that is not the only thing i mentioned. Consider that i.e. the AH brutosaur gave a significant boost to time spent in game concerning a not insignificant feature of the game (its auction house), and one can see more reasons why it would never be a (theoretical) lootbox exclusive.
The bottom line is simple: Does it provide material benefit? Then it's likely to breach the law concerning gambling if it's locked behind an RNG mechanic.
Mind you that Dutch law is not like American law where the word of the law is near absolute; effective locking would also qualify as locking, i.e. providing a deterministic alternative requiring disproportional amounts of invested time/skill would likely still be considered effectively locking behind RNG.
Added for clarity: "Material benefit" concerns benefits to things predating digital technology, as a rule of thumb, effort and time are two simple examples of that. This is relevant because newer laws are built upon older laws.