The reach should be the same as for your unarmed strikes.
Here are the rules from the Elemental Evil Player's Companion for an aarakocra's talons.
Talons. You are proficient with your unarmed strikes, which deal 1d4 slashing damage on a hit.
This means that the Aarakocra's talons are its unarmed strikes: an aarakocra makes unarmed strikes using its talons. The talons deal a different damage amount and damage type than normal for unarmed strikes, but they nonetheless are used to make unarmed strikes.
So the correct reach for the talons is the same as the reach for your unarmed strikes, which will be 5 ft as you suspected (in general, barring any other special features).
This is likely due to some sort of data entry/lookup bug in D&D Beyond, but only the developers could confirm that. It would be best to report this inaccuracy to the developers for correction. Regardless, treat your character's talons as having a 5 ft reach.