Indeed so - and understandable, given that when the first example of a type of product shows itself, the 'proper name' and brand name are unambiguously synonymous - until other similar products start to appear. I'm sure there are countless examples but, in addition to the Hoover and Megger which you mention, a couple of others which come immediately to mind are Biro and Henley (block).Often its the original or the most famous brand name that becomes the name of an object.
Life is sometimes amusing
Kind Regards, John