I did, admittedly, use it in Accelerate and Attack (and they do in Maneouver Group, so it was partly in thematic concert); in fairness, though AccAtt clocks in at 170 pages, putting it ahead of the MechCommander's Handbook but a good 80-100 pages under Total War. (I just realised my first fleet list book actually has a higher page count than the rules, huh.) So it's not really on the SFB level. (Though anyone alergic to rules that require more than one sheet of paper - I genuniely do not see the appeal of that level of simplification myself, because the only thing you CAN end up with is a dice rolling exercise - is going to be out off, but BT would put 'em off to, so I feel I'd be in good company.)
I don't remember precisely why I did it that way, except it does make for easier cross-referencing, though I suspect since I discovered how to better use titles and an index and the search bar in Word - and a though ToC - it's probably not necessary any more. (Never even occurred to me to do it in the fleet list book.)
You can, however, probably blame Rolemaster a fair bit, since that (and not D&D) was my formative RPG and that did use numbered rules.