I’m not so sure Arthur’s & Katherine’s marriage was so consummated- Katherine was devout & she swore it wasn’t consummated. I’m not so sure she’d have done sworn if it was untrue.
In those days, there would have been someone dressing them for bed, and it is known they were in bed together on their wedding night.
The morning after the wedding night, Arthur said to one of his servants, "for I have been, in this night, in the midst of Spain", and later expressed that it was a good pasttime to have a wife.
In his book on the wives of Henry VIII, David Starkey discusses the marriage of Henry and Catherine at length, and the consummation (or lack thereof) of her marriage to Arthur (or lack thereof). He also discusses why Catherine would later state her marriage to Arthur had not been consummated.
I tend to think, based on custom of the time, that consummation did occur, and Catherine lied not only because she viewed herself as the rightful Queen of England, but more importantly, she wanted to secure Mary's place.