This questions depends on our understanding of what morality/virtue (sīla) is. The traditional and I’d say commentarial (and even possibly ‘early Buddhist’) teaching, is the basic definition of sīla as the Five Precepts, but I find that problematic, as the conversation so far, seems to confirm.
Various consistent texts indicate the SE (fruit) is perfect in sīla (not SE path), the OR is improving samādhi (and paññā?), the NR is perfect in (sīla) samādhi (and improving paññā?) and the Arahant perfect in paññā. So all three trainings are complete for the Arahant. (see my study: https://www.academia.edu/1755108/Comparative_Analysis_of_the_Qualities_of_the_Sāvaka-saṅgha_Ariya-sāvaka_in_the_Suttas_-_excerpt_from_thesis)
If that is so, AN3.87 would be referring to the NR and it refers to training rules that are basic to the holy life and proper to the holy life. And the question may arise, which are those? In the First Council it said that the Arahant monks could not agree on what rules were to be categorized as major and which not. Major, for me, would be training rules that are basic to the holy life and proper to the holy life. So we might say, ‘the first council monks could not agree on what sīla was for monks’. To me that indicates they were not Arahants at all. (see my study on the supposed First Council: https://www.academia.edu/1755184/Comparative_Analysis_of_Three_Records_of_the_First_Saṅgha_Council)
The AN quote is more general than the Four Fundamental Rules for monks, as I understand them, which are, intentionally: killing a human being, sealing something of high value (I paraphrase as stealing someone’s livelihood, or means to a livelihood), sex with a woman and spiritual fraud (a very specific type of lying). All lesser types of bad action would be covered by the lesser rules.
If we take basic/fundamental sīla to mean the Five Precepts and the fifth to be drinking all together, and training rules that are basic to the holy life and proper to the holy life as the first one or two groups of rules for the monks, then the ‘sīla’ of the layman is more strict than the monk. For example, avoiding alcohol is one of the ‘minor’ rules of the monk; and where the First Precept is intentionally taking any living being’s life, in the first four rules for the monk, as mentioned, we do not find not intentionally killing any living being, but we only find not intentionally killing another human being and other harm or other living beings are covered in less important rules. So on for the other three of the Five Precepts.
There seems to be evidence in the EBTs that the Fifth Precept was added later, possibly as a drinking problem arose in the lay community. See the Kalama Sutta AN3.65 which seems to have ‘not leading others into such behavior’ as a fifth. There is also a sutta where Stream Enterers can drink alcohol and, it would seem, still maintain purity in sīla SN55.24.
My solution is, sīla for monks matches the first four training rules and next 13 rules only and ‘good habits’ cover all the other training rules. This seems to be supported by this vinaya text: Pārājikaṃ saṅghādiseso, ‘‘sīlavipattī’’ti vuccati. (falling from sīla) on http://tipitaka.org/romn/cscd/vin02m4.mul6.xml and lesser rules are called ācāravipatti (falling from good habits). Just as the Sigolavāda sutta (layman’s vinaya) talks of ‘the four vices of conduct’ and the rest could be called ‘bad habits’ if not kept. The Four Vices of Conduct match the First Four of the monks’ rules and the rest of the sutta talks about good habits for laypeople. (see https://www.academia.edu/6859436/Morality_-_Sīla_and_Sikkhāpada_From_Comparative_Studies_of_Pali_Texts)
It would be such a great blessing/boon if all humans could even just avoid killing each other! Thus would sīla protect society.