The correct word order in "Dear My Love"

The phrase "Dear My Love" is found in this page made by keepcalm-o-matic in the UK.

I would assume all English teachers say that possessive adjective always comes first, as in "my dear friend" and "my private idaho", and we never say "dear my friend". So the correct word order is possessive adjective, attributive adjective, and noun. Then could you tell me why in the UK saying "dear my love" is possible?

I have learned that, in a non-English speaking country, Japan for example, word order is sometimes off and people there usually accept both "my dear friend" and "dear my friend" as correct English. "Dear my friend" in particular is acceptable in their English and I suspect that's because "dear" in this phrase is not an adjective but an adverb to mean "with love and respect" (Merriam-Webster), or they regard "dear" as a preposition and mistake "dear my friend" for "to my friend". Is this type of misunderstanding also the case in "dear my love" by a UK designer? Or is there any other explanation?