IMO, many wish to be factual, and many consider it to be a legal issue, especially (potentially) with regards to the children. IMO, most expect MSM to be factual. Perhaps JS just misspoke, but I was surprised by the error, as well.
DB is married to SBradley, thus he is her husband. DB/JI have been portrayed as "fiancees". She and JI can't get legally married until her current marriage is dissolved. The current marriage has been portrayed to be still on-going due to lack of finances to divorce.
I don't know what the common-law marriage law is in MO, but I'd be surprised if it allows for one partner to be legally married to someone else.
Some may be concerned for the children's sake, regarding possible stigma about the living situation. I'm sure there are those that may feel judgmental about it, as well.