All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Scholars held different opinions regarding gifting the reward of good deeds to others as clarified in Fataawa 86828 and 88186. Based on the scholarly view that the reward benefits the person it is gifted to, then, apparently, gifting the reward to one person is not like gifting it to a group of people because they will share the reward; accordingly, each person's share will decrease, unlike gifting it to one person only.
Kashshaaf Al-Qinaa‘, a Hanbali book, reads, "It is permissible for the person to perform a good deed and dedicate all or part of its reward such as one half, one-third, or one-fourth to a Muslim, whether dead or alive. Both of them benefit from that and receive the reward."
This indicates that the reward is divided between the doer of the good deed and the person to whom the reward is gifted. Accordingly, the same applies when the reward is gifted to a group of people (it is divided among them).