I agree with this. When you do weight based calculation, you need the patient's weight, the dose in mg and then the concentration of the medication to give you the dose in mL. That's three places where you can make a calculation error (wrong weight, wrong dose, wrong concentration), not to mention the possibility for decimal error. The sheet at the bedside would have been a "weight based dosage sheet." This sheet will have all the doses for resuscitation pre-calculated based on the standard concentration of the drugs available, with the final mL calculation easily available.
Having the doses memorized vs referring to the sheet is somewhat a "generational" thing. It's now a practice recommendation to use the pre-calculated dose sheets instead of doing mental math because errors
are easy to make under pressure. (See this article for an explanation:
NursingALD.com - New Tool to Decrease Errors During Neonatal Resuscitation)
The older, more experienced nurse had the doses memorized because in her day, they didn't have weight based calculation sheets - you stood there and did the math on a paper towel or your glove or the surface of the cart. Do that enough times and it's just ingrained. When the practice change came, the older nurse retained that information, while the newer nurses haven't had time to absorb it yet. (And the older nurse seems like a wizard!)
The older nurse was also right that one SHOULD have the doses memorized, but the trend in healthcare is to structure things in a way that discourages you from functionally memorizing things. We used to do dose calculation by hand; now we are discouraged from doing that and told to use a calculator. We almost never prepare our own drug dilutions and drips anymore (pharmacy does). We don't even manually program most of our IV pumps. It's automated now. It wouldn't surprise me if newer nurses were told NOT to memorize and to always use the reference materials. All this is in the name of patient safety, and is supposed to take the element of human error out of things, but you'll hear a lot of nurses say that they feel like automation and increased specialization leads to a loss of skills.
(Since I have no wish to be a verified user, you can take this post as my opinion and not a statement of expert knowledge.)