I think this prevents confusion, first of all, quality mint condition depression glassware is hard to find due to the time period when it was made. If you're looking for 90 year old glass, or anything for that matter, it's hard to find non-chipped items. Also, the latter glassware has a charm of it's own, it doesn't need to be categorized as depression glass. I know there are some glassware books that call glassware from the 40s-70s depression glass, but to me it's not. In fact, several of these other books thank Gene Florence and use him as a resource, which further confirms to me who the true expert is. The 40s/50s/60s glassware was made differently, more automation, and it just doesn't sound right calling it depression glass. The great depression happened before World War II, not after. When I do searches for depression glass, whether on Etsy of the internet, and patterns that didn't start until the 60s show up, it can be frustrating as a customer.
Also, just a word of caution when buying. Make sure it's a reliable dealer, check feedback. Some patterns have been "copied" or molds purchased and used by other companies. Also, read the details, as stated above true mint depression glass is getting harder and harder to find each day, check the store's return policies. If you do collect, enjoy, it can be fun, and you'll find a lot of unique pieces. I have a couple examples of depression glass below.
This is a Queen Mary bowl for sale on Zibbet by CalloohCallay. The pattern was made by Anchor Hocking from 1936-1949. Even though the entire production time wasn't in the depression glass period, as portion does fall before 1940, so this is depression glass.
This is a Cameo plate for sale by BethVT on Etsy and the pattern was made by Hocking glass company from 1930-1934, making it true depression glass.