It's somewhat confusing that in the documentation and FAQ for FiveTran that FiveTran's "...philosophy is to make a faithful replication of source data with as few transformations as necessary..." and yet in that same core concept, it is admitted that you do not faithfully replicate source timestamps. In fact, source timestamps are forcibly converted to UTC. And if it doesn't have a timezone offset, it's loaded without timezone. That seems to contradict the philosophy of making a faithful replication of source data.
It also then puts the onus on the destination to keep track of what the source timezone was rather than allowing it to flow through and utilize timezone_tz and retain the original value.
Please allow for the proper mapping of timezone data to an appropriate type in Snowflake (and I'm assuming this happens with other destinations as well).