The issue is that priming bulbs don't meet the ABYC regulations for below deck fuel lines. Wouldn't be permitted in a new boat and could be flagged during a survey. If there's a fire and insurance company determines it was installed by the owner, it could be a problem.
Is there a logical reason why the ABYC believes the bulbs to be risky? It is easy enough to get bulbs from OE manufacturers that have been properly crimped to the lines and the connections are way better than clamped connections commonly found on the other end of the lines where the average boat owner routinely connects them to filters and tanks. Is it the flexibility of the bulb itself that causes it to be deemed risky? Or is it some dumb-a$$ed bureaucrat earning his living?
Also about insurance companies - it is a long held fallacy that insurance companies actively hunt down reasons not to pay reasonable claims. If a fire is directly caused by negligence, it may be good cause for a rejection but the fire would have to be caused by the fuel that leaked from the dodgy DIY repair, not for example from the galley stove and coincidentally there is a DIY connection in the engine room.
When it is all said and done, all insurance claims are derived from someone's incompetence, whether it be driving your car badly, leaving the front door of the house unlocked, forgetting your I-phone on the park bench, diving into the pool with your digital camera in your pocket, sailing your boat into rocks, doing your own maintenance, the list is endless and all of them will be paid out. Those claims that are not derived from human error are often named "Act of God" and this is the most likely
area of claim rejection.
Sorry, I'll stop now before this becomes a thread hijack.