What is the point of the heavy rule for squadrons? The way I read it, they are allowed to fly past squadrons even if they become engaged with one?

I know this probably isn't right so could any explain this a little better?

They can't engage enemy fighters, but they can still become engaged by enemy fighters.

Its a one-way street.

Essentially "Heavy" craft don't make good fighter screens because they aren't as agile as other fighters and they make easy targets for other faster fighters.

I believe it is meant as a detrimental effect as opposed to a beneficial one. Probably to lower cost of the squadron for what it does for you. Look at the X-Wing and Y-Wing basic units, X-Wing = 3 Speed, 5 Hull, 4 blue anti-Squad, 1 red Ship, bomber and escort for 13 points. Now Y-Wing = 3 Speed (Same), 6 Hull (Better), 2 blue anti squad (worse), 1 black ship (better), bomber (Same), Heavy (worse) for 10 points (3 points less). In my mind they were both trying to keep it authentic to the "fluff" of the Star Wars lore and trying to justify a good generalized ship for a low cost. Currently that is just my speculation though.

What is the point of the heavy rule for squadrons? The way I read it, they are allowed to fly past squadrons even if they become engaged with one?

I know this probably isn't right so could any explain this a little better?

Its the opposite way around, they can be held in engaged by other squadrons, but other non-heavy squadrons can fly away from them if they feel like it.

I believe skyhwk is correct. It looks like Heavy lowers the point cost of the squadron.

If a Y-wing squadron moves next to a TIE squadron and engages it, the TIE can move away from the Y-wing squadron because the Y-wing has the Heavy keyword. Usually squadrons cannot choose to leave engagement.

And a point of clarification on the OP mentioning "flying past" squadrons - it's only the starting and ending point of the movement that affect engagement. Let's say you have the following setup:

T=TIE, X=X-wing, Y=-Y-wing

T ____ X __ Y

The idea is the Alliance player is trying to screen the Y-wing by flying the X-wing in front of it. But if the TIE has sufficient movement, it can completely bypass the X-wing, leaving TIE engaged with the Y-wing but NOT the X-wing. It would end with the setup like this:

____ X __ Y T

You probably already know it, but I just wanted to be sure.

I think it is as the other people have commented. the heavies are the somewhat slower bombers so they can be used to attack ships better than non bomber fighters. but if fighters protect the ships they will need escorts or protection.

I think that is the intention of the heavy and escort rules anyway.

The point is that the rule is supposed to be a negative for the Heavy Squadron, not a benefit.

Think of "Heavy" as "you're so slow and unwieldy that enemy squadrons can run away from you."