If the flip has a completely unrelated version, it's most likely a repress. In the 90's it was quite common to have the b-side related to the a-side but not providing a clean version ("Mix 2", semi-accapellas, mixes with vocal snippets from other cuts, etc.) and this was probably to prevent unauthorised use of the riddim. For example Penthouse was notorious for never providing clean versions and at times other big labels like Digital B did it as well. Can't remember Jammy's being one of those though.