LAN A–-----------------LAN/pfSenseA/IPSEC-----------------------IPSEC/pfSenseB/LAN---------------LAN B
Don't get confused that it looks like a seperate Interface up there. IPSEC is completely transparent between the two pfSenses once established, it doesn't cross the WAN interfaces even (seen from the packetfilters view).
As I said you only can control incoming connections on an interface. So the rules at the LAN interface of pfSenseA determines what can move over the IPSEC to pfSenseB. pfSenseB can't block connections incoming over IPSEC as it's not an interface seen by the packet filter. The same applies for the other direction. Rules at LAN interface of pfSenseB can pass/block traffic going through the IPSEC to pfSenseA only.
I hope this makes it a bit more clear.