The answer is simply that the PSC is designed for professional services and the ECC, for example, is designed for the building of works. The obligations and requirements of the contracts and their scopes are therefore very different. Each contract will refer to different matters that will be dealt with within the scope. Therefore, each example scope has been written for the specific contract, or more correctly, the type of works, services or manufacturing that is involved. So, if you look at the example scopes for the NEC4 Term Service Contract (TSC) or the NEC4 Supply Contract (SC), you will see that those too are different from those in the ECC and PSC and each other.
Where there are similarities these are treated in similar ways and using similar numbers. So, for example, design by the contractor or supplier in the ECC, TSC and SC are covered using similar headings and the same S300 number. But that is not the same in the PSC, as sometimes the design is the whole point and therefore is integral to the scope. But that is not always the case with professional services and therefore design may well be irrelevant. For example, you would expect a structural engineer or architect to design, but you would not expect a lawyer or accountant to do so. It is for the scope itself, not the contract, to set that out.
Where the PSC and the ECC are similar in their requirements then similar terms are used, see for example ‘Description of the works/service’, ‘Accounts and records’ and ‘Transfer of Rights’. Finally, you need to bear in mind that these scope layouts are a suggestion only and are entirely optional. You do not have to use the layouts when writing your scope, but you must ensure the scope covers all relevant matters within them. Clients are often let down by their scopes, which can be far from being the ‘complete and precise statement’ required in a good contract, no matter what the contract is for. That is why the term ‘complete and precise statement’ is used in the guidance for each and every NEC4 contract.