How good and pleasant it is when brothers live together in unity! It is like precious oil poured on the head, running down on the beard, running down on Aaron's beard, down upon the collar of his robes. (Ps 133:1)
Everyone needs community. It is particularly essential for new monastics, who are entering unknown territory. In St. Benedict’s day, it was the duty of the abbot and the more experienced monastics to guide newer seekers as they trained the heart, mind, and body to heal the soul. In our day, authority is more widely dispersed. A monastery may be made up of five or six seekers, who confer together in order to increase their understanding and improve their practice. The key point here is that in order to foster spiritual growth you need to consult with others.
Another strength of a community is that it helps you sand off your rough edges when you rub against the rough edges of someone else! And of course, loving thy neighbor requires neighbors. Your Benedictine practice group is the shallow end of that pool.
I appreciate your point that even a small group of only 5 or 6 can significantly support spiritual growth if they (1) actively share and consult with each other, (2) are committed to reliably being present for each other and (3) follow a reliable guide (in this case, the Rule of Benedict). I would add that it's all too easy for such groups to become book-study groups or prayer groups or social groups if they don't keep a clear focus on Benedictine practices in day-to-day life.