These super-wide cassettes are getting a bit ridiculous, at least for anything roadies would sanely consider. They are suggesting using 11-13-15-18-21-24-27-31-35-40-45 (whereas stock is 11-13-15-17-19-21-24-27-31-35-40).
OneUp says the modified cassette yields two distinct shifting 'zones' - one with smaller gaps for climbing, and one with bigger gaps for descending
While that might make a kudge workaround for 1X chainrings, it does not seem at all useful otherwise. For more serious climbing gears, I would reduce my granny to a 28t (we currently run a 48/30 x 11-32 for extended or steep climbing) before even considering the standard 11-40 mtn cassette on a road bike. By comparison, the gear spacing on a 11-28 11spd cassette is our preference for standard riding.
Spec' Tarmac (road), Spec' Secteur Disc (commuter & tourer), Salsa Mamasita (MTB), CoMo Speedster (tandem), Surly Big Dummy (cargo), Airnimal (folder), a train pass, and NO car :)
We're running the XTR 11-40 cassette on our tandem, with 30-46 chainrings. To make the spacing better, I got a 105 12-25 cassette and used the first two cogs from that to make it a 12-40. The steps on that have proved to be just fine for us, and it's great that it fits on our 10-speed freehub body. Shifting is with a SRAM Rival 11-speed shifter and X9 "10-speed" rear derailleur, which works just fine. I can't imagine needing the 45 tooth cassette cog unless we wanted to use a compact (34-50) crank. BTW, we live in Switzerland, so most rides involve significant climbs.