welcome to the forum !
I think the problem with lists of horses to follow is that it's tempting not to evaluate the races they ran in that earned them the flag nor the race that they're due to run in next time out. In other words if you just get a notification that a horse you've bookmarked to follow is running tomorrow it's tempting to back it just because it's on your list of horses to follow without looking more closely at it's real chances
I think it's a similar problem with Stable Tours that you get at the beginning of each season or basically trainers opinions full stop. They might know a lot about the horse in their yard but they don't know much about the ten other runners in the 3.15 tomorrow, ie the ones their horse is running against. It might be tempting to back a horse because the trainer has singled him out in his pre-season stable tour but there's no context of the race he's running in and the other horses he's running against