False. No problem with expressing.
HOWEVER - there could be a problem at 6 weeks if you express to bottle feed baby EBM instead of doing night feeds for example. Night feeds are important for milk supply therefore missing out breast feeds could reduce supply which can cause problems with hungry baby.
Expressing doesn't necessarily make breastfeeding easier - it can take longer to express than it does to feed. Baby is much more efficient than the pump at removing milk.
A lot of mums aren't very successful at expressing initially and worry then that they don't have enough milk. This has a knock on effect on success of breastfeeding.
I personlly think that all breast feeding mums should express milk and store it in the freezer for future use. All mums should be taught how to hand express instead of buying expensive pumps.
Until breastfeeding is established - ie mum is confident in latching baby, nipples are fine and baby sucking well, then expressing to give bottle feeds should be avoided.