The "Battery on the concrete" myth stems from the wood case battery days. I'm no scientist or engineer but it was explained to me that a wood case battery would discharge if sat on concrete. I'm skeptical of tranny fluid changes myself because a drain and fill wont get it all out. Drain one all day, pull it out, disassemble it and drain it and the converter and measure it. Just seems like a waste...tranny flush is different. If you only changed one fluid other than the oil I'd vote brake fluid all day. Probably wouldn't hurt to change the diff fluid every thirty years or so.
I hear about not jump starting new cars regularly and washing new engines too.