I've asked multiple peach mains about this since they were all DI'ing the throws correctly. All of them including Armada said that they were reacting to the throw. My whole game play for awhile revolved around this mix up and it completely stopped working. Simply holding down is enough as well for both throws from what I remember. Tested it awhile back but I believe that DI got out of follow ups on both throws.
I'm going to assume that they aren't reacting for what I'm about to say, for the reasons I listed above. If you want to believe otherwise, that's completely fine.
Because of the down DI, the default should pretty much always be fthrow. If they DI down, you dash attack them, get them above you and **** them up. If they DI down and away, you techchase (nair to cover tech in place, then react to other options)
I'm 100% not saying to rely on the mixup, but if you notice that they are doing their DI down and away to avoid the dash attack and take the techchase instead, you can dthrow fsmash if they DI as such.
If you don't get the read and they DI down, then you're in an edgeguard situation.
Again, this is assuming that they aren't capable of reacting, which is what I believe for the reasons I gave above.
Thanks for the info about the down DI by the way.