Do leases for Sept. move-in really get signed in March/April?

I'm planning to move to Boston in September, and I've been talking to a potential roommate who went to school in bos and knows the whole deal with renting. She told me that September leases get signed in March/April??? I'm from the southeast so here you can find something in two months and move in. I get that Boston is a college city and very competitive in terms of housing, so I wouldn't necessarily be surprised especially at the time we're planning to move. We're looking at Back Bay, so maybe signing dates vary by popularity of neighborhood. Just wanted to get more of a consensus if anyone has intel

Edit: thank you all for your responses, I'm now sufficiently terrified of the boston housing market :)