We have easily walked up to both.
Boathouse, just a couple of weeks ago, party of 6 was seated immediately at 6pm. There were ZERO open table reservations available (I checked often right up until we arrived at DS) yet there was plenty of tables open for walk-ups. BTW I am incredibly anxious about seating and we were very far from other tables and felt extremely comfortable.
Homecoming always saves tables for walk-ups, too, and the wait has been minimal here recently (esp for patio). They are not on Open Table.
That said - in that dining glitch a week or so ago, those restaurants did not cancel on all the additional tables so I wouldn't be surprised if some of the walk-up spots they typically have will be lessened due to absorbing so many extra reservations for the next couple of months.