Could be. The "regular sweet Molasses" I mentioned is not sulfured. It is the other Molasses used for cooking, baking and flavoring. Un-sulfured Blackstrap is the cooking Molasses that is bitter and its use is very specific and it should not be used unless the recipe specifically calls for it.regular sulphured molasses will kill microbes not feed them.
Back to the use for plants, both the sweet and Blackstrap are a Molasses that is not sulphur treated. The sweet comes from the second boil, contains more sugar, a lower concentration of minerals and lower levels of salts. The Blackstrap is from the 3rd boil, contains less sugar, has a higher concentration of minerals and has a higher level of salts.
It may be that the sulfured stuff will kill microbes. But Sulfur is a necessary nutrient needed by plants and it shows up on the "leaf problem" charts that are commonly used to start diagnosing problems.
The Oaksterdam University has an article on this and they say it is sulfur dioxide that kills the microbes. Reading up on this, it is the sulfur dioxide which is problem and not any sulfur itself. Also, of the 3 types of Molassess, light, dark & Blackstrap, it is possible to find all of them available in either sulfured or un-sulfured. Ripe sugar cane or sugar beets will naturally produce sweeter Molasses and the sugar itself is a preservative.
Choices, choices, which Molasses to use.