I've re-used barbs and olives a couple of times on my R685 (levers)/ BR785 (calipers) with no issues. Always ended up being at the caliper end. I've got the spares and been ready to fit them if necessary, but haven't died yet.
Yes, I think Shimano are erring on the side of caution.
I can't see why you couldn't slice the tube to free the connector and Hope (I think) say their olives are reusable.
@Scilly.Suffolk started
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I've re-used barbs and olives a couple of times on my R685 (levers)/ BR785 (calipers) with no issues. Always ended up being at the caliper end. I've got the spares and been ready to fit them if necessary, but haven't died yet.