When buying direct through Disney you haven't had to do the second step of making reservations separately from ticket purchase since a little bit after reopening last year. You choose your dates for both single day and multi day now during the purchase process.
Speculation on mine and the part of others is that this was to eliminate the problem early on of tickets being purchased and no reservations being available.
But also you're not locked into those dates. The ticket is valid for at least a year from purchase date. So for those that want to buy direct, but the dates aren't open yet (but will open within a year), the tickets can be purchased with placeholder dates and then those reservations cancelled and not remade until the desired dates open. Doesn't work with single day unless you're really sure what tier that day will be. But works well with multi day.