But in many more words..

But I said more things too.
I guess that not having English as primary language is the disadvantage I have to deal with. Maybe that's why I don't get likes when I explain the same thing?

 

SO on the T0220 package the bottom die with the metal IS THE PRIMARY heat transfer surface, BUT heat is also radiated from the opposite (top) surface. So a second heatsink can radiate some more heat. I have also seen heatsinking attached to the upper surface of that metal tab, and certainly that has some effect. Knowing if it is cost-effective is a separate issue.

 

SO on the T0220 package the bottom die with the metal IS THE PRIMARY heat transfer surface, BUT heat is also radiated from the opposite (top) surface. So a second heatsink can radiate some more heat. I have also seen heatsinking attached to the upper surface of that metal tab, and certainly that has some effect. Knowing if it is cost-effective is a separate issue.

Yeah, but if cost-effective is a separate issue, I would go with a copper heatsink and good termal paste and applied very thin, with good pressure and forced air cooling. This is doable, there are lots of AliExpress copper heatsinks for sale.
Because if you need to dissipate through a smaller area than the back, and after 3+ mm of epoxy, I think you're screwed. No matter what heatsink you put (on the front), the junction will remain hot.

 

The heat should be conducted AWAY from sensitive, critical areas of the semiconductor ASAP. That's why I asked about the benefits or drawbacks of my frontal heat sink "mod" (in addition to normal rear heat sink conduction). So if that front heatsink is drawing heat into it, that might not be ideal because it will PULL heat into it thru critical areas of the transistor that would not have experienced that heat if I ONLY used the (normal) rear surface .

 

The heat should be conducted AWAY from sensitive, critical areas of the semiconductor ASAP. That's why I asked about the benefits or drawbacks of my frontal heat sink "mod" (in addition to normal rear heat sink conduction). So if that front heatsink is drawing heat into it, that might not be ideal because it will PULL heat into it thru critical areas of the transistor that would not have experienced that heat if I ONLY used the (normal) rear surface .

Why would a separate heatsink that's only in contact with ambient air would put heat into the package? If it isn't touching anything hotter, it's dissipating, not heating the package up.

 

The heat should be conducted AWAY from sensitive, critical areas of the semiconductor ASAP. That's why I asked about the benefits or drawbacks of my frontal heat sink "mod" (in addition to normal rear heat sink conduction). So if that front heatsink is drawing heat into it, that might not be ideal because it will PULL heat into it thru critical areas of the transistor that would not have experienced that heat if I ONLY used the (normal) rear surface .

Heat sinks do not PULL heat.
Heat sinks conduct heat away from hot areas and move it to colder areas. They dissipate heat.

 

The heat should be conducted AWAY from sensitive, critical areas of the semiconductor ASAP. That's why I asked about the benefits or drawbacks of my frontal heat sink "mod" (in addition to normal rear heat sink conduction). So if that front heatsink is drawing heat into it, that might not be ideal because it will PULL heat into it thru critical areas of the transistor that would not have experienced that heat if I ONLY used the (normal) rear surface .

No, if anything, it will pull heat from the surface of the silicon that otherwise would have had to travel through the junction to get to the metal tab and be pulled out the back.

 

Heat sinks do not PULL heat.
Heat sinks conduct heat away from hot areas and move it to colder areas. They dissipate heat.

"Conducting heat away" is very commonly referred to as the cold area "pulling heat" from the hot area and/or the hot area "pushing heat" to the cold area.

 

Heat energy ONLY travels from hotter areas to less hot areas. At least in all of the areas where the fundamental laws of thermodynamics apply.
That includes the real world.
"All systems tend to move to the minimum free energy" THAT is how I have seen it described.