Related Settlements TYA IHT Charge

Hello,
I am looking for clarification of the related settlements rules when calculating the TYA and exit charges for trusts.
If, say, 4 trusts are all created on the same day by the same settlor with £10 they are related settlements.
At a later point the settlor adds £125k to each of the trusts on the same day. The assets qualify for BR so no IHT on settlement but on the TYA the assets are not BR assets.
There are no previous chargeable transfers as the £125k settlements were added on the same day and I understand that the Same Day Addition Rules don’t apply to related settlements (IHTA84/S62A(4)) but if that is incorrect please advise.
If we say on the TYA each trust is worth £225,000, for the purpose of the TYA calculation do we include the value of the related settlements, as the initial £10 per trust (so £30 total in each computation) - in which case the hypothetical transfer value is less than the NRB (£325k) and reporting limits (£260k) - or does it include the added £125,000 per trust (£375k for all three trusts) - so the hypothetical tax charge exceeds the NRB and there is an effective rate of tax applicable to each of the trusts and IHT will be due?
Guidance I have read and legislation only refers to the value after commencement of the related settlement, so just the £10, and any added property or increase in value is ignored but this allows each of the four trusts to retain an (almost) full nil rate band which seems contrary to the related settlements and same day addition rules so I feel like I am missing something.

Thanks
Kat