Adobe Document cloud: file shared to 1 user, but forwarding invite allows others to also open file

Within Adobe Document cloud, a single file was shared directly to one users' email address. That desired user was able to open the file successfully. I found out that if that user forwards their shared file invite email on to other users, then those other users are also able to open that file. Is that normal? I thought that a direct share to email address process was more secure than providing an "open public share link". Thanks in advance for any comments.