its pretty funny here
on one hand - everyone doesnt think twice on spending super amounts on "dekorashan" on the same car, but when it comes to oils/coolants etc.. everyone wants to paint with a "choonay ki koochi"
the reason to mention the diff viscosities of oils is to give some choice to customer, e.g. a customer maybe stuck in timbuctoo and only have one of those oils. It can be used but also read the fine print to see for any anomalies from control specification.
e.g. if the 0W20 is not meant for continued high speed driving, DONT go full bore down the motorway nonstop at top speed. btw - another fun fact, The 0W20 toyota is selling in the USA actually has a hot viscosity of near 9.5 cst - which is very close to the 5W30 viscosity of other regular branded 5w30 oils.
on the same note - M1-0W40 has a hot vicosity of 13 cst, which is at the very cutting edge of the high scale of an xW30 viscosity of other oils. The area where the 0W40 is a champion is shear strength and stability. Please note its also not regarded as a "clean burn oil" - its blended with really low ZDDP to save the 4 kittens in mercedes benz/BMW/Audi sedans.. Them felines are spensive - about 1200 euro to buy. benz refilled ones run about 1200 dollars in the USA.