What is the authenticity of the statement that Islam forbids slaughtering an animal in front of another, and that doing so renders the slaughtered animal’s meat unlawful?

The jurists have agreed upon the reprehensibility of slaughtering an animal in front of another, and this is part of the perfection of Sharia and its mercy. However, this act does not prohibit eating the slaughtered animal if it has been slaughtered according to the Sharia method, because it is merely a reprehensible act. As for mass slaughter in automated abattoirs, there is no harm in it, because the animals do not see each other during slaughter, and it is permissible for a Muslim or a person of the Book to pronounce the name of Allah once when operating the machine with the intention of slaughter.