They underestimated how quickly people would take off the headphones and jump on the bandwagon to claim affinity with an injured celebrity.
Are you suggesting they should have engineered the voice actress' voice to be more distinct from another actress they were considering for the part? Or just not gone near it with a 10ft pole? because if the latter the studios can just release a new Her and Him movie with different voices in different geo regions and prevent anyone from having any kind of familiar engaging voice bot.
Apparently they had no confidence in defending themselves, so why even release with the voice in the first place?