I commend your fortitude for engaging with HMRC tech. Do you want a job?
If your scheme allows you to take benefits before the normal pension age and the early withdrawal isn't due to extenuating circumstances, ill health etc, your LTA is reduced by 2.5% pa to reflect the premature crystallisation. However, with AFPS, your LTA isn't reduced because the scheme is one which is protected.
It's saying that if you retire and crystallise benefits before normal pension age of fifty, because you're in AFPS, you're subject to protection.. not that the LTA doesn't apply in the wider sense of it dropping. And you can then be demobbed and continue to accrue benefits to the normal LTA of the day with Virgin, BA etc.
Osborne is likely to reduce pension tax relief for HRT Payers from 40% to c.25-33% for everyone, on March 16th. He won't want to alienate the heartland so I wouldn't be surprised if he raises the LTA again (before 2020) to appeal to them. He may even decide to do away with it completely, giving someone else down the line the chance to earn kudos by once more, reining it in.
Plus ça change, plus c'est la même chose.