"Code" and "Name" in the Polish Baptismal Certificate?

As some point, my father acquired an original certificate of baptism for one of his uncles that was born in Poland. At a later point, he showed that certificate to an "expert" in Polish genealogy who told my father that, because of the way the baptismal certificate was worded, he could tell that our family was a member of the gentry.

Has anyone else ever heard of this?

I have looked at that certificate and another certificate of a great uncle from that family (and therefore, may have been written in the same parish). Both those certificates were slightly different but used a variation of the phrase "filius legitum" which I believe is Latin for "legitimate child". Also, both those certificates named both parents.

I compared those certificates to another I had from Poland about the same time period. The other certificate did not say "legitimate" child. It just said "filius" and it named only the father. Also, it described the father as a "laborer". (Neither of the first two certificates gave any indication as to the occupation of the parents.)

Was there an actual convention that baptismal certificates for the gentry were worded differently from the working class? Or are the above differences just a difference in wording between parishes?

Is that what the expert said classified them as gentry? There are from what I have heard signs that relatives may or may not have been gentry. For example the term land owner was a give away. Most baptismal records I have seen contain both parents names, some even contain the grandparents as well as witnesses.

Merged: Baptism

Why would my grandparents names be on my baptism certificate. Different surname to that of my mothers.