The phrase "all hetero" is synonymous with examples of the literary devices of modifiers. The phrase strictly clarifies & classifies a statement as heterosexual (not gay), that potentially could have been viewed as heterosexual or homosexual. This is differentiated from no homo or no bruno, in that these two phrases are used to clarify the heterosexual intent of an otherwise homosexual statement. However, the phrase "all hetero" can be used in a "no homo statement," but not vice versa (as a "all hetero statement" may not have been homosexual in the first place).
"The wind blew me today; all hetero." The wind could be personified as either male or female, thus "all hetero" is used.
Not an Example:
"Suck my dick," when said male to male, should include no homo as opposed to "all hetero."