[tialaramex]

The credit card transaction involves fungible currency, the Bitcoin transaction doesn't do that. As a result the batch operation succeeds for the credit card.

Six equivalent cards, each performing six offline transactions for $5 each results in thirty six $5 transactions, $180 from one account to various merchants. Settlement transactions can complete more or less instantly or take several days, you don't care and your card isn't involved.

[prvit]

What’s the issue with Bitcoin in this context?

[tialaramex]

The credit card transaction isn't about the specific money. A Bitcoin transaction about this Bitcoin A is different from one about this other Bitcoin B. If I do two offline transactions paying with Bitcoin A, but keep Bitcoin B each time, then even though I received goods worth two Bitcoins, the blockchain says only one merchant gets Bitcoin A and neither gets Bitcoin B. But if I do two $100 credit card transactions, those aren't for the "same" $100, when settlement is completed two $100 transactions adds up to $200.

[prvit]

Yes, but a reasonable bitcoin wallet wont let you spend the same coin twice, even if offline. As far as I know, none of the common wallet software that support offline transactions will let you do this by accident.

Credit cards suffer from a similar problem, the transactions will not necessarily go through when you get online.