Hi - I am experiencing the same issue and wondering if a resolution was ever found.
I think I am understanding the error correctly. The condition within the if statement is checking if Matches, a data frame object, is equal to a string ("ALL"). This returns a Matches-sized data frame of trues and falses, but the if statement requires a single boolean value, e.g. length of 1. The length() of a dataframe is number of columns, which in this case is > 1.
My only thought is that I somehow have an outdated version of the function even though I installed the package today and have tried updating the package, since others have used the command successfully. However, the version shown in my Packages tab is 0.1.0, the same version shown in the screenshot from the official StatsBomb guide that martin linked above.
Did you ever contact or hear back from the author?