One stop long haul on same ticket within 24 hours pays the Same tax levels.
Self connect adds risk and is effectively tax evasion.
Other than the legal cost of recovery outstripping the tax take value -You could risk a visit from the revenue.
Those frequent travelers ARE monitored however most tend to value time accept the bribes(miles, or similar awards) rather more than inconvenience of a break in their travel arrangements.
Preclearnce really isn’t such a benefit given the extra journey leg imho.
As to transiting Dublin the actual numbers of such passengers is rather smaller than many think - it’s a little over a million yes rising however not a statistically large element of the airports overall terminal passenger numbers close on thirty million a year.
Oh and much of the current growth is being generated from mainland Europe rather than the UK.
No the vast vast majority of UK -Dublin traffic remains point to point..