No, the green label doesn't need a blocker for mrv.
SWM is kind of simple. No internal splitter. The switch listens for a control signal on 2mhz. When a receiver powers up it claims its swm channels based on the number of tuners it has. There are 9 swm channels. 8 for video and 1 for the APG. Any receiver can use the APG when it needs. All 9 channels are modulated on the coax. Kind of like cable tv when you split it, all swm channels are sent to every receiver. The receiver ignores the channels it didn't claim when it powered up. When you change channels, the receiver tells the swm, hey I need 101 TP 30 on my swm 4 channel. So the switch takes that transponder and downconverts it to swm channel 4. Your receiver takes the signal and picks out the video stream you requested.
So you can see, it has nothing to do with splitter ports. You actually want the least amount of splitters for less loss on MRV. I have seen some setups where a swm16 was used and two 8 splitters were on each swm leg. The loss of the cable, splitter, swm16 internal mrv bridge, then the other 8 way was to great for mrv to work. We ended up consolidating stuff down and put the HR34 by itself on one swm leg and the other receivers on the other leg. And with the swm16 you can not put more than 8 tuners on each leg.
Sent from my C64 w/Epyx FastLoad cartridge