Hi Claudia,
I haven’t seen the question to which you’re referring, but I will try to provide some information without that context.
AFOs generally block ankle plantarflexion ROM to facilitate foot clearance during gait. Regardless of footplate length, I think it would be expected that AFOs will block PF ROM. I did find one article indicating that AFOs with full-length footplates produce increased stance phase PF moments compared to no AFOs (wherease 3/4 footplates were no different than no AFOs). That same study found that AFOs with 3/4 footplates resulted in significantly less than normal dorsiflexion in late stance. It was hypothesized that AFOs with full-length footplates increased DF ROM and PF moment in late stance by delaying or impeding heel rise more than the 3/4 footplate.