It's nothing personal from the banks, but you need to remember that banking is a risk management game. It is profitable, but you need a licence from a regulator to play.
Regulators put obligations on licence holders so that the government's policies and the laws are enforced. If they don't comply with those obligations, they lose their licence and cannot make any profits.
How each bank implements or operationalises its obligations may vary, but that is a function of risk tolerance within a given bank.
The problem you're facing here is that you want to move not insignificant amounts of
cash. Governments don't like that being done, so they put obligations on Banks to prevent it.
To be honest, dividing it up into 5k lots is likely to be more suspicious to the bank than if you were to transact the entire amount.
It would be a pretty unsophisticated bank that was not able to detect the type of movement you're contemplating. Just
keeping it below a certain threshold (in this case 5k) will be unlikely to avoid attention.
It may be true that 100k is above the transaction reporting threshold, but 5k is below. But that is only considering one type of reporting. Other AML reporting obligations include suspicious or unusual transactions, which do not necessarily have threshold amounts.
A better option may be to reframe your arrangements in a way that allows you to restructure your transactions to a more reliable method of transferring the funds.