strictly speaking you're right. My statement is more along those lines:

http://www.ijstr.org/final-print/nov2015/Comparative-Analysi...

"Although, the tensile strength of steel is 2.5-3.0 times higher than bamboo and the specific gravity 6-8 times that of bamboo; but by counting their tensile strength/unit weight (bamboo vs steel), the tensile strength of bamboo is 3-4 times that of steel."