Our system was different in the UK (9-10 math courses per year for 3 years), but students knew if they were pure or applied by the end of the first year and by the end of year two you knew more specifically what research you would want to do for a PhD.
The US system has so many fewer math courses as part of a degree (maybe 15 required though I guess a strong student might take more) that to get a decent level of preparation I think you’d want to have at least half of them (probably most courses beyond analysis if you are well ahead of the regular sequence) being increasingly specialized in one area.