Ofsted do not warn schools. They arrive, inspect and deliver a judgement. Lots of myths about inspections still alive around this thread.
Ofsted would be more like an MOT if they did not have lots of evidence and data over several years before they turn up. This is why schools that are showing they do not get enough progress from the children are likely to have an early inspection compared to those whose children fly. This is why some schools are inspected fairly reguarly and others may not have been inspected for 8 years.
Since 2015, the inspections have changed to look at far more data. Any inspection prior to late 2015 is not under the current handbook. Therefore a report from 2013, for example, may be rather useless if there has been a complete change of staff and the school has 50% more SEN children for example. Recent inspections are far more reliable for any parent and the school improvement plan arising from an inpsection is very important to improve what may be wrong. Also, parents want different things from schools. Parents at small village schools like the "family atmosphere" but fail to notice their children make slow progress because they have bought into the ethos of the school rather too much. They may value that side to the school, but Ofsted will look at far more hard evidence. Any school that thinks they can wing an inspectinthese days without knowing about pupil progress in some detail, is just fooling themselves.
Security and accessibility is a very unusual reason to be SM. As you say, August, the report "claims other things". All these other things were innaccurate then? How do you know this? Have you looked into the data? If other schools really think a school failed on locks and gates they are sorely mistaken. It is just tittle tattle I'm afraid. My guess would be some poor teaching, assessment, lack of progress progress and leadership were also in the mix. I would love to know the details of any report that put a school into SM due to site security and accessibility (presumably of disabled pupils/staff) but found excellent teaching, superb progress and fantastic leadership. I think the "other things" were significant but you have chosen to ignore the obvious shortcomings. Ofsted didn't. Regarding security, schools that have high absence rates, pupils absconding and pupils who are removed from school to go and get married may well have security issues that need to be addressed. Depends on the school. Any Ofsted training for Governors always flags up the flavour of the season. At the moment it is PP spending and outcomes and value for money.
When you look at the schools, User 453, check to see what their progress is like on the Govt web site. Ask the Head for details of how they teach Maths and English. Look at some books. Ask the Head what the current challenges are. Do they have a largely stable staff with a blend of experienced and younger staff? Ask what they have done to improve. How successful has it been? They should be open and honest with you. Try and see some teaching. Does it inspire you?