Rummy vs blackjack question

I recently read the Wizard's report on Costa Rica. He talks about the game of Rummy. (link here/games/rummy/) I had some questions that I e mailed to him received a response that I should post the questions here. Here is what I sent:

In your description of Rummy you have an some early surrender options that
differ from regular Blackjack options. I don't understand why they would be
so different. For example in regular blackjack you have:

Dealer ace Vs. hard 5-7

but in Rummy your chart says only to surrender a 7 vs. a dealer ace. Can
you explain the discrepancy ? I don't see a difference in early surrender
with a 5 or 6 vs. and ace in regular blackjack and rummy. Can you double
check if this is correct? (no I am not doubting you, but I am, lol )

Other rummy issue is that you can usually draw to split aces. How does that
change the chart? Just looking at the A,A vs A hit feels so wrong, as does
doubling 7,7 vs. a 3 but I can grasp the concept. Numbers don't lie.

Thanks to the group for looking at this.