Actually, Detros has a point. If the defenders have enough point defense to withstand long ranged fire, even AMM fire, everything but point blank, within 5-second travel time fire, then a forward defense would force the attacker to close to effectively zero range to transit past them. Unlike a conventional defense, where the defenders would expect to be at some range from the attacker (depending on tech level), but certainly not 10,000 km where they could shred them in seconds.
The conventional jump point defense, a slow beam defense fleet might just not do enough defense before the attacker got out of range. But a forward defense, as long as they can win the beam duel at any range, they have enough firepower to prevent a transit.