Yes, that's exactly why. As people "walk past" the current date to when they want to stay, days open up behind them.
Say I want to book Nov 3rd. If I grab 7 nights on Oct 15 and walk them forward, nobody can beat me out of the room.
On Nov 15th (11.5 months out), I grab 7 nights Oct 15-22nd. Now, nobody can step in front of me until the 22nd because I have at least that one room occupied. And if nobody can get that room during the time I hold it, then nobody can use that room as part of their 7 night reservation.
On 10/22, I can call and cancel the six nights behind, and add 6 more ahead until the 29th. And then on 11/3, substract and add until I have my 7 nights starting 11/3.
From the moment I held the room on 10/15, I prevented anyone else from stepping in front of me until my reservation was walked into place.
You have to have that first day to book multiple days and that first day is tied off from my earlier booking.
In practical terms, if I wanted 11/3 and tried to start walking on 10/15, then I have multiple chances to grab a room at 8 am.
If not avail 10/15, I have about 17 more mornings/chances to secure and walk to my 11/3 reservation. If I'm successful on any of those days, then I can hold that room until I walk it into place.