Steam cooks more quickly than boiling in water. It all depends on what kind of device you're using: a decent purpose-designed steamer will heat 500g in no time - 10-12 minutes. A stove-top double boiler/bamboo stack may take a little longer.
I find it takes longer from frozen in the streamer than in a pan of boiling water TBH I normally do a quick defrost in cold water first and go for the 7 min option
My grandparents always cooked veg until they were succulent and appetizing. Not like today's practice of hard warm unappealing salad. The nonsense the 'experts' spin you in order to avoid paying the gas/electricity bill for cooking ! One can digest the nutrients better in well cooked plantlife.