It will still cycle the boiler much more than a storage based system,

On what do you base this article of faith?

It is based on the fact that a storage based solution will be able to
perform a considerable amount of secondary loop heating service before this
activates the vessel thermostat, allowing the boiler to perform a slightly
longer more efficient burn.

With an instantaneous combi, the combi must fire every time the secondary
loop pump activates, and in the worst case, if the loop circulation is slow,
it might even be below the modulation threshold, so it might even have to
cycle to maintain primary temperature, although careful design can eliminate
this.

Therefore, even in a best case scenario, the instantaneous combi fires every
time the loop thermostat calls for heat, whilst the storage based system
could service for hours without boiler assistance, with sufficient capacity
and thermostat hysterysis/double thermostat.

Christian.