styleHtmlContent is the same regardless of the value being true, 'true', false, 'false', 1, 0, '1', '0'. These all equal true. Only null makes it false. The docs says the default is null but it also claims it's a boolean which I don't think it is -it's a little confusing.
Do you have an example of where you are seeing this? There is a falsey check on this and we will for a forced Boolean on apply. As far as the documentation goes, I'll check if the parser can be changed to properly handle that as null has a special meaning within the library and is used to improve instantiation performance.