I do recall mention somewhere on these boards of a lower saddle straining the quads more without putting the hamstrings under stress, meaning that the quads develop but the hamstrings don't. Is it possible this could carry over into daily life, such like my problem above?
Well, you spend a lot of time sitting. At work, at home, and on the bike. Almost certainly tight hip flexors. Stretch them. Probably inactive glutes, from tight hip flexors. Do hip-ups, single-leg deadlifts, or something else glute-dominant. Probably tight and overactive hamstrings (synergistic dominance). Stretch them.
Essentially, you're doing an isometric squat/deadlift while stooping to garden. The glutes are supposed to be active at the bottom of the ROM, and when they aren't, the hamstrings take up the slack.
I've done stretching on doctor's recommendation for legs, shoulders, arms, etc. and I'm pretty well convinced that stretching is quackery.
It ain't exactly quackery. The hamstring complex has been extensively studied at this point, and it does work for them (and that's significant). For other structures, though, it isn't always so clear. It you apply it indiscriminately, it doesn't work right. You should really only be stretching tight structures, which takes an actual functional assessment. Otherwise, stretching is ust a somewhat effective inhibitory technique.