You really don't understand. The tokens are frozen because otherwise there's no way to build a reliable distribution lists. Aggregating and subsequently calculating the ~120k and growing addresses that have an EOS token history takes time. And in that time, transfers can be made, and thus invalidate the snapshot. In order to have a 100% verifiable snapshot and to ensure all value is properly transferred from the ERC20 token to the EOS native token, the tokens must be frozen at some point in time.