There seems to be a lot of confusion here about DHT but most of this info is here with a little searching, but I'ill try to address two points here.
Firstly, regarding systemic DHT inhibition from taking topical S-Equol, yes it can happen but you have to look at the numbers. For example a 5% monixodil solution is 50mg per application, the new topical finasteride people where going on about a while back was something like 20mg if I recall correctly. However the amounts that actually get absorbed into the skin is a very small fraction of what is applied and the systemic amount a fraction of that fraction. So the 0.25mg of S-equol per application as described in the patent is really small with the amount that goes systemic is going to be really small also.
Secondly, about DHT level in blood serum, scalp etc. Note that DHT and T are present in non-balding hair follicles, in a balding follicles DHT is elevated around 200% and T reduced by 50% or so and DHT in scalp hair is also around 200% of normal.
Now finasteride will reduce blood serum DHT to 30% and but scalp DHT levels drop to around 100% of normal, why is that? Because your hair follicle is generating 5aR that converts T->DHT and it seems that Finasteride can not stop T->DHT in the follicle, which I know to many seasoned contributors is quite controversial.
The logic behind this is that your scalp DHT should drop to serum DHT levels if Finasteride was doing it's job completely, however as the your own hair follicles are still producing DHT your scalp DHT only goes down to the normal level.
For most people this will be enough to stop or slow down balding, however Finasteride does this by not tackling the root cause of follicle 5ar production but by decimating your blood DHT levels there by reducing the overall DHT that attaches to the AR receptor in your hair. It is also the reason why topical finasteride has to go systemic for results.
Now, getting back to S-Equol. S-Equol inhibits DHT by attaching itself to the molecule so that it cant fit onto the androgen receptor. The hope is, that whilst 5ar inhibitors do not seem to work in the follicle, S-Equol may stop the resulting DHT produced inside the DP cells in the follicle from attaching to the androgen receptor. If this is the case then it could explain why only 0.25mg is required.