Textbooks and reviews of textbooks often argue about whether objects should be introduced early or late. The argument for introducing them early is that they are fundamental, and programmers need to get acclimatised to them and avoid bad habits. The argument for introducing them late is that they are an advanced topic to do with the organisation of code and data, which makes no sense until you understand pretty well what code and data are.
Both arguments are sound, and both approaches can be made to work in a controlled setting with teachers present. That means that either approach can be used in a conventional textbook.
However, in a do-it-yourself tutorial of this sort, material needs to be introduced in linear, bite-sized chunks, without forward references. The fact that objects are complex with a lot of different aspects to them means that there is really only one workable approach. That is to introduce objects gradually. They have to be introduced early because there is a lot to say. A deeper understanding cannot emerge until later, because of the amount of groundwork that needs to be covered.