It's definitely a myth that my town believes in - anything at all means they need solids. Oh their hands are in their mouth they need solids! Oh you are breastfeeding you won't be able to keep up with her she will need a bottle and solids.
I think you will know when your baby will need solids. 'We didn't start solids until she was 6 months and she didn't really start to enjoy it until 7 months.
You are the mum - you will know what is right.
I don't have any advice to what to say to others because they generally won't listen to you anyway - smile and ask why they would start solids early and where they got their information from. Smile and say you will consider it.
Good luck!