One of my special interests is history of infant feeding and advice and practice related to it.
Your description of what was done is pretty accurate, though things were changing then in some maternity units.
Four hourly feeding was still recommended as the norm, even though research had shown it seriously undermined breastfeeding.
Babies were kept in nurseries and were left to cry between feeds. Mothers fed them in the nursery every four hours. The usual routine was 10 mins a side, not 20 mins a side, but you worked up from that, starting at a couple of minutes only on the first day. The babies were normally only brought to the mothers if the mothers could not get out of bed.
Use of formula top ups was very frequent, either between feeds or after feeds. Earlier than 30 years (say 40s and 50s) milk was not formula, but diluted and boiled cows milk with sugar added.
I have old midwifery textbooks which describe these rules.
Breastfeeding rates fell considerably, with the introduction of almost universal hospital birth in the 1950s and 1960s, largely because it could not succeed when these strict routines were placed on it. Mothers soon lost heart because it was just not working, and if their babies were not happy on 6 feeds in 24 hours, 10 mins a side, they assumed they did not have sufficient milk (and they probably did not).