If you read the article you linked, you will find that is not true. From the article: "between 2016 and 2020, there were seven sexual assaults against females in women's prisons by trans women." 7 assaults in 4 years is not 5x more.

If you are referring to the statistic that "trans inmates are 1% of the population and commit 5.6% of the assaults", you will find that the trans inmates in question are actually trans men being incorrectly housed in women's prisons.

From article:

“there were 125 trans prisoners in 2017, 60 of whom were serving sentences for sexual offences. Of those 60, 27 were serving a prison sentence for rape.” which is more shocking than your 5x statistic. Note the 5x statistic appears weak to me because “Between 2016 and 2020, there were seven sexual assaults [reported] against females in women's prisons by trans women.”.