I guess the yoghurt might be free due to other nutritional stuff- calcium/protein (if there is any...can't remember)/fibre etc.
i personally do syn everything that sw tells me to syn. why? because it works! if you don't, and it doesn't affect your losses, that's great. our plan is what we make it. some people have 2 big slices of wholemeal as a healthy extra rather than just 1. some people don't cut the fat off bacon and don't syn it. if they do that then that's ok, as long as they are happy with what the scales are saying every week.
For me (and this is just me) I pay £49.50 every 12 weeks to work the sw plan and get the support and guidance i need. if i'm meant to do something, in regards to syns, healthy extras, amount of superfree on my plate, etc, then i do it. and I can safely say that it is working pretty well for me. I'm happy at losing on average 2 1/2lb every week.
Yes I do have slip ups, yes I do mess up from time to time, and I suffer with low losses on those weeks. But for the most part I stick to the plan that I am basically paying to do.
I've been on sw for 9 months and there are still a lot of things I don't get and a lot of things that I probably won't understand. For those things I just accept that it must work, because others have done this plan before me and achieved amazing results. I like to keep things simple- overthinking isn't worth the hassle.
So I can't answer your questions- but I can say from experience that what they say does work.
There is a contact button on the SW site- if you have any questions or queries you can email them and they should give you the info you need
