They can't have a common bottom heat plate that is also the electrical conductor. That would result in a 1S pack and also prevent the pack from being isolated from the chassis. A thin insulator will not majorly impact performance as it's effect can be negated by a greater temperature differential (just like the current side cooled cells).
The small bond wires are a critical safety feature to limit current in a single cell during a fault.
While cooling from the bottom favors the anode/ copper electrode (assuming a classical negative can and positive top), this is not a huge deal since the cathode and anode have a huge surface area to transfer heat and low layer to layer thermal resistance.
Cross section: Anode, Separator (wetted with electrolyte) , Cathode
...ASCSASCSAS...
http://blogs.cuit.columbia.edu/yanggroup/files/2018/08/1-39.pdf
A typical separator has a thermal transfer coefficient of 0.19W/(m*K) whereas the cathode and anode layers (including active coatings) have much better values of 2.0 and 1.06. Combined with their thicknesses (S:24, C:82, A:106 um), this results in a total value of 3.47W/(mm^2*K). Even better, recall that the cathode is sandwiched on both sides, so we double this value to 6.94W/(mm^2*K). (Even better, the anode and cathode values are edge to edge and we are only going half that distance, but let's be conservative)
Put simply, for every 7W of heat a square millimeter of cathode generates, its temperature will only rise one degree Celsius above the anode temperature.
To put it in perspective: Say charging is 90% efficient and all loss is heat (tabbed are going to much better than this). A 2170 is around 4.8Ah at 4.2V or 17.3Wh. At a 4 C rate that is less than 8 watts of heat for the entire cell. Thus, the temperature delta between adjacent anode and cathode layers is less than one degree. The area scales with cell diameter resulting in the flat charge time vs diameter plot.
Where tabbed cells run into issues is that the anode also needs to transfer heat through the separator (or along itself) to the tab or can edge and the sandwich effect does not exist (all heat moves in the same direction for a region) so this temperature rise happens multiple times.