Frozen/blocked Pitot/static and frozen AoA probes are two different situations. In frozen Pitot case one ADR is kept for stall warning which comes from AoA probe and not for pressure data like speed, altitude etc. When AoA probes are frozen at lower speed and aircraft accelerates to higher cruise/Mach the alpha prot threshold decrease to appx. 5degrees of AoA while the system is getting higher frozen value and that can trigger Alpha prot protection based on this erroneous data. So the only way to get out of the hard protection of normal law is to get into alternate law by switching two ADRs off. The third is kept to give you speed but if Pitots are also blocked that will also be incorrect. This AD is not very comprehensive and doesn't cover both frozen Pitot and Pitot together can mislead the pilot if Pitots are also blocked. A320s which have MOI153528/P12909 the FPV is modified to calculate FPA from hybrid GPIRS(mixed IRS and GPS position). So you can use it in this case. But without this MOD bird can only be used provided Pitot/static is not blocked and that is why the wording "FPV consider".