I had understood that if the person saying hamotzi does not say b’Reshus, then everyone must say their own hamotzi. I think the kitzur shulchan aruch says this. Are you saying that there is an opinion that does not follow this?
Shalom, Thank you for your question. I am unaware of the law in the Kitzur Shulchan Aruch you are referring to – if you could send me the reference I would be appreciate it greatly. The halacha is that if the person making the blessing over bread has in mind to say the blessing for all those present, and those present have in mind to be included in the blessing of the person making the blessing – then, if they hear the blessing being said, they are included in the blessing and do not need to make their own blessing. This is all true even if the person saying the blessing did not ask for permission to say the blessing by saying “B'Reshut”. The custom of saying “B'Reshut” can be found in the Shulchan HaRuch (Orech Haim, 167,14) where the Rema writes that the person saying the blessing should say these words first. This is a sign of respect, to ask those more important than us for the permission to be the one to say the blessing for everyone. The Mishna Brurah explains that even though it seems that the reason to ask for permission to say the blessing by asking “B'Reshut” would not apply if the most important person was saying the blessing, none the less as a sign of modesty, even in such a case it should be said. However, the practice of the Vina Gaon was not to say the words “B'Reshut” ever, (see Ma'aser Rav 78) – he believed that these words could be a forbidden break between washing and saying of the blessing over the bread. It seems to me that there is a widespread practice to only say the blessing, and not B'Reshut. In any case every one agrees that leaving it out does not effect the blessing over bread for all those who intend to take part. I hope this is of some help. Blessings.