I found that the previous descriptions of this route lacked definite start/end landmarks, so here's what I propose. On the Golden Gardens side this route starts/ends at the terminus of the bike path at the official green sign that says "Burke Gilman: Begin." No need to cross the street or go all the way to the beach -- the trails over there are technically not the Burke Gilman. On the Blyth Park side this route starts/ends at the eastern most edge of the bridge over the Sammamish River. No need to touch any sign or structure since there are multiple.
I created a new Strava segment to reflect this route under the title "Burke Gilman - Golden Gardens to Blyth Park." No offense, but the previously established Strava segment and the submissions here seem to have slightly inaccurate, arbitrary, or poorly defined start/end points, and obviously it would be useful to be clear. The points I've described are within the length of the runs that everyone has submitted so far, so no one will be found to have retroactively DNFed, and the time of my own submission overshoots the end point enough that I'm confident I won't be perceived to be manipulating the route to my own advantage.
Anyway, a real Northwest classic.