In addition to the other points, some airlines give 1.5, 2 etc. times the miles for J v Y. You could contribute those miles to future business travel, if you need to 'add value' - either in the form of a ticket, or an upgrade from Y.

The most common reason I see for justification of J is [discounted J] is less than [full priced Y]. I don't think J really ever shows as cheaper than discounted Y, but it quite often shows less than full fare Y. I play along with a few folks who use such a justifcation and whilst I don't entirely agree with them, that is the fault of poorly worded travel policies IMO! The 'perks' J would give, that you can demonstrate a cash value for, include things like lounges (cost of meal, able to work online with free wifi, telephone calls etc), free luggage allowance for checked bags, and the 'soft perks', things like priority security access (saving time, meaning you can spend more time at the office / with clients), cost of hotel room overnight (ie you sleep on the plane), able to work in private on the plane (sensitive documents etc), arrive rested and able to work immediately, showers on arrival so you don't have to pay for day use of a hotel room when you arrive etc.

Frankly, I wouldn't worry about it. The company policy is 7+ hours and I would leave it as that. I don't see any reason you should be held to a different standard than everyone else.