You are putting together quite a reference library, Boggy!
I looked at that first table and thought, "There's nothing for me except beets and chard! There's no way carrot seed will germinate in July!" Then I notice that there are 2 parts to the table .
Still, lettuce is in the same boat with the carrots. With so much sun here in July and early August and so much aridititididititid . . . it . . . dryness -- shallow-planted seeds won't stay moist and germinate.
I'm happy enuf to call something I plant on June 15th, a "fall crop" but what's the deal with "snap beans?" They must be only talking about pole beans.
I can plant bush beans right up until July 15th. At one time, I thought I could plant anytime in July but failing to pick any beans before first frost in 2 years out of 3, convinced me otherwise .
July 20th or August 1st shouldn't be the date certain for planting lettuce, spinach and mustard family seed - unless, one wouldn't be happy with a 6" or 8" plant. Mustard, bok choy, choy sum, fun jen, etc. can take some frost easily and appreciate cooler fall weather, anyway. Even lettuce can take a light frost. And, spinach can be overwintered even with sub-zero winters. I can plant them a good 2 weeks closer to first frost than suggested and won't be sowing them when there's soooo much heat.
I'm really trying to stay on schedule here at home and that's . . . just my 2.