We’re talking about syntax that was perhaps used at that time (of inscription) for subject of great import. Many languages have various dialects for specific purposes. I believe the Japanese language has a dialect for business use, one for home use, maybe more than that. Olde English is found in many historic documents from England and America, when it was still new to most of the earth.
“Olde English”
Never existed. Maybe you mean Old English (sometimes called Anglo-Saxon)? If you mean older English forms - when people used ye, thou, thine, and the like - that was simply early modern English not “Olde English”.