Well, I am a catholic and I think it sends a wrong message.
In the past when catholicism ran deep in catholic families and there was antagonism between all christian denominations, then a catholic marrying other than in the church was deeply shocking, and seen as a public rejection of the church, so coming back and having a marriage in the church, ignoring anything previous, marked a return to the catholic 'family' someone returning to regular mass, taking part in church proceedings
Nowadays it is very different, especially in the case of Boris and wife, Boris was baptised a catholic because his mother was, but that is as far as his catholicism goes, he did not grow up in a catholic family, he did not go to catholic schools, he was confirmed into the CoE, he has never been a practising catholic, and he has 2 previous wives and documented lovers.
His wife was baptised a catholic, as was their son, but I know little of whether she was brought up a catholic or sees herself as a practising catholic.
Perhaps I cynical, possibly heretical, but I cannot but wonder whether the two of them resurrected their catholic heritage and had their son baptised because by doing that Carrie Symnds could have the big white wedding and walk up the aisle in style because, I suspect Boris was disqualified in some way from marrying in a CoE church.
Personally, in this modern day and age I think the catholic church should require proof of their return to the faith they were baptised in before they are married in a catholic church, for example going to Mass every Sunday for a year not living together, and remaining celibate until the marriage.
Current catholic procedure needs revising.