Perhaps "proper" was not the best choice of words. I think it is an optimal way to top balance for DIYers but by no means the only way. Whatever the manufacturers do works for them and the purchasers of those batteries. They have the equipment to bin and match cells easily. Cells that are matched in capacity are inherently balanced at least in the beginning.
I really don't think they match the way you think they do. They may verify cells are close to the ones before and after which should be very close because they were made in a batch, but switching between batches is where I see a potential problem. The cells we get are not always in order of production and thus can very. Capacity testing every cell is not possible in a production environment.
Have you seen how they form the cells initially? My understanding from pictures is there are rows and rows of cells being charged and discharged as part of the "forming" of the cells. It can take days for big cells. The data from that process is how they are binned. How else would they maintain quality? It is my opinion that most of the Alibaba cells that we see come from the results of that binning process.
As I mentioned earlier, the surface area with the least resistance is the terminal top. Far from limiting Amp draw, the resistance of the stainless stud and nut (Ohms law) will mean that most of the current will flow through the terminal top.
I have a Heltec 300A 8S BMS and am very happy with it, but no idea whether they offer a 24S model.
That is a power supply. It will charge (at 3A), but has no end-of-charge circuitry.
