By referring to 'choke point', you seem to be suggesting a physical restriction to the flow rate.
The specified flow rate for each media, is the amount of flow that quantity of media is able to support while effectively filtering out whatever contaminants the media is intended to remove. It is not a physical restriction but is an indication of the flow rate in which the media may no longer be fully effective.
If your water requirements are higher than the media will support, assuming your water system is capable of delivering that higher flow rate, then it is likely that some of the contaminants the filter is expected to remove, will pass through the filter and be present downstream at each plumbing fixture. As the flow rate is further exceeded, more of the contaminants will pass through.
Please keep in mind the backwash rate required by most filter media, is often greater than the service flow supported. Your well, pump and plumbing setup will need to constantly deliver the flow required to backwash the filter, for the entire backwash cycle.
What makes you think you require 13 gpm downstream of the filter & softener? If only because you're considering a 2 cuft softener, that is the highest flow rate that amount of resin will be able to supply 0 gpg. That doesn't signify that is the SFR you will actually need or will use.
Most residential applications usually involve modest flow rates (<6 gpm) with a higher than usual demand needed on occasion. Backwash filters are typically sized to satisfy the usual household needs, often due to water supply required to backwash the media. If a reduced amount of whatever contaminant bleeds through during an occasional higher than usual demand, it is usually not an issue.