A gem promo theory, injustice 2 mobile

I was thinking, a fresh hero have 6 chances for levelling offer and an unlock hero offer ( total 7 )

And it takes the old 5 chest pull to a gold 5*  hero.

5 x 160 = 800 total shards

160 3*
200 4*
440 5*

With the gem promo cost for gold hero

360 gems for 100
900 gems for 200
2700 gems for 440

In theory for the farmable golds like aquaman can be obtain via promo for a cheaper price.

Just needed to collect the remaining 740 shards. But since we can only have a maximum of 7 chance.

7 x 100 = 700 shards from ( 2*-3* promo) and farm the remaining 40

7 x 360 = 2520 gems needed

Vs the intended 360 + 900 + 2700 = 3960 gems needed.

That's 1440 gems saved.

The downside is that you need to max out your hero at 60 and waste 6 weeks to trigger the offer at 2*. Also this only works for 2* gold heroes. That quite a lot of effort to save up 1440 gems.

Next is to use the 3*-4* offer ( some gold hero can use this method ), which only need 3 weeks ( 2 if counting the hero unlock offer ) with the cost of 2700. With a remaining 40 shards to farm. All challenge, arena and campaign gold hero benefits from this as they require mandatory time investment to acquire them traditionally. This saves 900 gems.

So why go all the trouble of doing this ? Saving gems ? I'm just curious if this theory works. Ways to save gems is always interesting but it is effective and efficient way?

For Science !