All my Sealion books (Tim Venning, 'Eternal Caesars', 'Caesars of the Bosphorus', 'King Henry IX', 'King Charles or King Oliver?', and 'Bonnie King Charlie' ) are written in 'History' style. The 'King Henry IX' and 'King Charles or King Oliver' books were in fact originally written as part of a continuing series, the first following on from my Medieval and Early Tudor Britain books and the second from my English Civil War book, published in print (HB) by Pen and Sword to 2015 - a delay in their moving onwards for several years led to me then trying out the ebook route with Sealion from 2018. History-style narrative is the way that I am used to writing history or CF and I have always stuck to that since I started my Alternative History of Rome CF as a teenager , and I did this for my non-CF history books too. Ditto for assorted unpublished novel style books; I have just not got used to writing in a first-person persona, and haven't done it right from my teens onwards.
It has also helped me to stand back from the action and put in editorial comments, and to switch narrative 'streams' more easily when I am dealing with one situation featuring multiple characters' stories.