As it takes two/three days for the milk to come in, surely they baby gets the colostrum in the first feed or two whether that's 30 minutes after birth or 48 hours after birth. If 48, surely having some formula first, doesn't negate its benefits.
Like all things pregnancy, birth and post partum related, this sounds like another mantra, trotted out with no clear basis by mw's and hv's. A statement such as, "well Jane, if you decide to exclusively formula feed, your baby won't get any colostrum which passes antibodies from you to them and has other benefits. It would be good to breastfeed at least two to four times, but I have given you the information and it's your choice.
My DC are 31 and 27. I still recall the utter clap trap most midwives chatted about bf and how contradictory it was. Ditto the HV who trotted out the mantras but when asked about the research, the best she coukd manage was "oh, I don't know, I can only tell you what's written in the leaflet" A leaflet aimed at those with little intellect and which cited nothing.
Having said that, I'm surprised my DC survived looking at today's guidance:
Had a regular G&T or glass of wine when pg (obstetrician said it was fine and FAS occurred in alcohol dependent people)
Napped with them cuddled up to me on the sofa.
Used what is now probably a rudimentary car seat and they slept in it if they dropped off in the car.
Weaned at 3/4 months (GP's advice though)
Failed to breast feed ds beyond 8 weeks and due to what mw's and hv had to say on the subject was made to feel an utternfailire and developed pnd.
In their own room from day 1 (with DD moved into the nursery with her until 6 weeks).
Allowed to cry so I could have a shower, dry my hair and get dressed.
DH had no paternity leave and I coped from day 8 with both.
Made up bottles for 24 hours in advance (according to prevailing guidance).
Didn't have the dc weighed or see an HV after the second visit. She was rude and useless.
Booster seats in the car from about 2.5 years.
I have a dgc on the way and shall be staying very silent although dil seems sensible about it. Happily she's eating some meat and they haven't found out the sex. They are several thousands of miles away and interference will be limited but so too will help.