As I said, we have guidelines from our providers
That's just a cop out, are you a white label?
Ask your provider what is so damn special about NetEnt slots that you want to steer players away from them with a "stick", and dangle a "carrot" to get them to play others.
It could also be viewed as dishonest marketing, as saying slots count 50% is a way of making a 60x WR look like a 30x WR to make it more palatable to players. This is really a "con", as it makes it harder for players to make comparisons between different casinos. An honest casino would quote the higher WR, but at least they would not sneak in this 50% weighting on slots. Players could then make an informed decision, such as play elsewhere with a 30x or 40x WR.
Given that this is all hidden behind an invisible link only makes it look worse, as though you went to considerable lengths to keep this information from players, but could still claim that it had been published should an issue arise.
ALL slots should count 100%, it's the only fair and honest way to advertise the WR of a promotion, use a well accepted and understood benchmark, which in the case of online casino is the slot game, with other games weighted in relation to the slot games.
Excluding an arbitrary list of slots is also going to confuse most players, especially the recreational ones who just want to go in and play. Unless you understand the inner workings of the games, all slots are the same type of game, and suggestions that some slots are somehow beatable calls into doubt another well understood concept, that online slots are all completely random, despite appearances to the contrary, and that one is just as likely to win or lose no matter what slots one chooses to play.
If a few slots can be beaten by smart players, evidenced by the exclusions and weightings, then there is more to playing them than pressing spin. This brings us into the realms of the UK Fruit Machine, games that are NOT random, and can therefore be beaten by a skilled and observant player. It seems that in your case, ALL NetEnt slots have been cast into doubt, suggesting that they are 100% "better" for the player than your other slots, which means that conversely, your other slots are "crap", so why play there when one can seek out another casino offering these NetEnt slots counting 100% towards WR.
We have yet to see an operator explain WHY some slots are set to less than 100%, or excluded. I'm afraid "we have guidelines from our providers" looks like there is something to hide, either to do with NetEnt slots, or these "other" slots that count 100%.
The reluctance to explain makes it look like these other "crap" slots have been designed to a much lower RTP than the expected and accepted norm of around 95%. It's certainly something your provider would want to keep under wraps as it would negate much of the marketing efforts. Indeed, getting software providers to reveal the TRTP of their slot games has been like getting blood from a stone, yet at the same time we are told such information is "unimportant" or "not properly understood by players". If this is so, why the efforts to hide it from those who ARE interested, and who might even understand what the figure means?
Leading a consumer to believe something about your product that is not true is against advertising rules in the UK. This can even be due to the omission of information, not merely the issue of misleading information.
It does seem that quite a few players are specifically seeking out these NetEnt slots, and are not really interested in the others. To them, this 50% weighting hidden behind an invisible link is seen as an attempt to mislead.
It also seems that this dubious practice is confined to the browser based multi provider casinos, so there is something a bit odd going on that has nothing to do with the games themselves.
Maybe you have revealed what it is in your statement, these platform casinos don't think for themselves, they do as they are told by the providers, even though it is merely a "suggestion", whereas the download or single software casinos have managers that can think for themselves, making their own rules regardless of what others using the same software do.
To the player, it draws a picture of a white label, crap CS that can't authorise anything, left hands not knowing what the right is doing, and altogether a second rate place to play compared to a single supplier casino that does everything in house, making it's own decisions.