Hi Rob
You're right, that range feels very different at the upper and lower limits. Quoting from the article...
"114-140bpm is “Recovery” for, well, recovery rides and similar
141-153bpm is “Aerobic” for long rides to improve endurance and efficiency"
So yes, the lower end of it really does nothing in terms of training benefits, except on the day following a hard training session it would provide active recovery - ie it would have the same effect as sitting on the sofa but might encourage more blood flow to the legs and hence help the body's process of repair and recovery. 130-140 is still pretty easy once you're warmed up, but 3-4hrs at this pace and you'll know you've done a ride - especially if you're riding alone and hence are maintining this level of effort ALL the time. Once up into the 141-153 band (Zone 2), I have to work at maintaining it; if I don't concentrate I slip below it, but if I remind myself to keep working then it's a good steady level which creeps upwards on hills. So, going back to your point, yes - you can ride at 110-120 while smoking a fag, but (unless it's just a recovery ride) if you're training you really want to be up in Zone 2.
To be honest it's one reason why I do a lot of my training rides alone; in a group you'll be spending a fair bit of time cruising. For me that's certainly not because I'm quicker than the rest, it's just that (as you note) it's only really when you're on the front that you're working. As an example, last ride I did was just over 3hrs, HRave was 139, 1hr30min in Zone 1 (mainly 130-140bpm), 1hr10min in Zone 2. Legs knew they'd been out and about, though it's worth remembering that this kind of riding is still very much just about base fitness - efficient pedalling, training your body to avoid burning up glycogen stores, and getting used to sitting on a bike for hours. Proper suffering comes later!
Tony Williams (on his Flamme Rouge site) notes that his power meter showed that on club runs he was freewheeling for something like 20% of the time, and - if you've limited time for training - why waste it? However... ...group training rides, and the chaingang, have their uses too.
Would be interested to compare notes with you Rob on what you've got lined up training-wise with your return to hostilities this year. If we've similar HRmax there maybe some interesting comparisons (tho of course I'm nearly 10yrs older...
)!