Because the amount is irrelevant - whether the player deposits 10 quid or 500, should he/she win they'll be caught under the dupe a/c rule (I refer to the non-disclosure of sister sites not with the same casino) and then the FU term will come into play. Same aggro, same BS.
What I can say with the UTMOST CONFIDENCE is that should anyone win on one site and then be FU'd because they were SE at another site under the same license AND the casino had failed to list the relevant sites in their terms/bonus ad terms
at the time you joined and deposited then regardless of any IBAS ruling to the contrary you WILL win in a civil court:
Terms must be 'complete, comprehensive, fair and relevant' and therefore the onus is NOT on the player to click a link to an outside body or business that contains information that is vitally important and therefore should have reasonably been expected to have been included at the point of sale.
If you heard the R4 article today
even IBAS agreed (although this may have been due to the publicity).
So if you win a decent amount, live in the UK and were FU'd by any casino that did NOT have sister sites included or present in the terms when you joined, sod IBAS - just go straight to County Court and summons them. The casino is in breach of basic consumer law and this will always be upheld and have 10x more clout than any ADR/IBAS decision - the loser can give the middle finger to either of those if they wish. If these casinos even try and contest your case it's bordering on the vexatious as your argument is essentially outlined in statute.