Also, it is wrong to call any church a "pseudochurch" (unless they are something like Pastafarian). Just because they have different beliefs than you do, does not mean that they are a false religion or church, even if they consider themselves to be part of the Christian faith. Different sects of Christianity believe different things, including what marriage is and whether marriage can be between two men or two women or involve more than 2 people. Christianity, at its core, is simply believing that Christ is the Messiah who died for your sins and believing in his teachings, it doesn't necessarily mean that a person has to believe every part of the Bible. Also, their ceremonies are just as valid to them as your religious ceremonies are to you.
Plus, as I said above, there are a lot of couples who get a legal marriage before they have a wedding ceremony, but they still have both and would generally consider refer to their wedding as the ceremony, not the simple signing of their license.
And common law marriages are even recognized by the IRS.
Common-law marriage - Wikipedia, the free encyclopedia
Common Law Marriage
Common Law Marriage
Marriage is both a personal and legal institution. Being involved in either is all that is needed for some to consider a couple as married. The legal is all that is required for the US government to consider a couple married. And, there are some religions where the personal is all that is required to consider a couple married. Most couples have both.
BTW, many common law marriages afford many if not all those same government benefits.
Christian - Wikipedia, the free encyclopedia
Christian - definition of Christian by the Free Online Dictionary, Thesaurus and Encyclopedia.A Christian (help·info) is a person who adheres to Christianity, an Abrahamic, monotheistic religion based on the life and teachings of Jesus of Nazareth as recorded in the Canonical gospels and the letters of the New Testament. "Christian" derives from the Greek word Christ, a translation of the Hebrew term Messiah.
Notice how none of those definitions include the necessity that a Christian or a church that claims to be Christian must adhere to everything within the Bible, only the belief in Jesus as the son of God and his teachings.