Thanks for this. Though various ball types appears to be within the ITF guidelines. I wasn't sure if a tournament was permitted to change ball type or not. So instead of publishing the ball type, perhaps the ball brand should be made known/recorded, if it isn't already.
Yeah, it's not talked about much, unless you get some moaning from a player, or it changes at a slam. There is an ITF/ATP factsheet that goes out for each tournament with the exact ball used though, been that way for at least a decade I know of (got copies going back that far anyway!). So it's not exactly hidden .... but neither is much made of it.
With regard to Indian Wells: the "slow" rating was the previous, from 2009 iirc. They get recertified every few years, so possibly if it's about on the border then natural variation means it'll alternate between slow and medium/slow. I'd agree it's probably a slower surface than Miami most years, with IW's desert air compensating a bit (although Miami seemed especially slow this year).