To a certain degree it is. It also depends on the chemicals and additives used in the ATF. They often contain additives to protect against corrosion, and contain detergents and dispersants. Water can bind at the molecular level with these chemicals and additives and also form suspensions.
You can easily test with a drop of water and a capped jar of ATF. Mix and shake and observe what happens. Does the water drop "disappear"? Does the solution become cloudy? Can you see two liquid phases?
This is for guns, right? The ATF being the ideal gun lube came out of an article written by a gunsmith several years ago (forgot the name). It did not come from a lube expert and the article had several flaws in it.
Motor oil has far higher levels of AW as well as corrosion fighting chemistry. ATF is an inferior product for guns. SL rated oils will have higher levels of ZDDP. M1 high mileage would be ideal for an off the shelf option.