I could see both sides of this argued and would say this is very much a table dependent area. One thing is not to get hung up on the "Ritual" in the name, since that is just the commonly accepted form within the Order, used to avoid giving away hints of an individuals process such as "Potion" or "Charm" would.
In favor of allowing it: It is not a "ritual" or "spell". It is something designed to "re-energize" or "recharge" an enchantment (this was part of the argument in the last LR thread and in the Aegis thread in how it interacted with a LR). Penalizing a character with a flaw for spell casting with the inability to renew a LR expands the flaw.
In favor of not allowing it: While not a "ritual" or "spell", renewal is still a short process taking roughly the same time as a ritual and using Vis. If the flaw does not feel restrictive enough for its value, blocking renewing a LR increases that restrictiveness.