Trading expenses would be synonymous with transaction costs IMO but maybe not under GIPS. Transaction costs are only the costs that it takes to actually BUY/SELL securities. The big emphasis from that section was that CUSTODIAL costs, are NOT included in transaction costs, even if it's done by a per share basis (can see them throwing this curveball at us)

I think there's a difference between saying bundled - ESTIMATED deductions and bundled minus KNOWN deductions. (provision 2.A.14). If you can't say for certain what's a transaction cost and what's not, that's why you would reduce it by the entire amount. Provision 2.A.13 is not making any reference to deductions. It's simply saying, if you believe transaction costs are X, go with X.