Do solutions only get deployed to designated WFE's?

When a solution is deployed to a sepcific webapp does it by design only send to WFE servers?

What about for a globally deployed solution?

I recently added a server to my farm that was not intended to be a WFE, but when you add it to the farm it automaticaly

becomes a WFE, so I  stopped the SP Web Application service and it removed all the IIS sites and all seemed well

Now I am seeing tha Global Solutions are still deployed to the on WFE servers, is this by design?

The non globals seem to be retracted from the non wfe.

Now when I retract a solution from a non WFE that still has the solution deployed to it the retraction doesnt work(since its not a WFE)