Generally... a cracked block is going to keep having problems regardless of how you try to fix it.
Expansion/contraction tends to break the repair. Drilling the ends of the cracks is to hopefully
prevent the crack from growing. If you don't actually drill at the end of the crack... you did ZERO good.
Cast iron tends to crack right beside a weld. The material in the weld will never have the same thermal expansion ratio as the original casting.
Epoxies tend to crack loose due to difference in thermal expansion.
You might be lucky and it work for years. This is far more rare than the repair failing within a few cycles of heating
due to normal operations.
As I said... its problematic at best.
Sure... try the repair. At least it can make it work for a while.