I think the exact pattern depends on the specific school and whether applicants with offers are likely to have a preference for other schools.
Some schools, particularly those as you move to mid-tier expect large numbers to turn them down. Obviously they hope they won’t, but they know from experience that they are actually second choice for many. This can be especially the case if lots of the applicants are hoping for a state grammar place. The difficulty is that it can differ year to year. Such schools first of all significantly over-offer. They have to, to ensure they aren’t too dependent on WL. Even the most popular schools do over-offer more than people imagine, as even applicants to top schools have usually applied to several and some will choose an alternative in the end due to travel or scholarship or bursary etc.
Schools don’t like using the WL. If they can avoid it, it’s better. It’s because by the time you get to the close of acceptances and then a few days in, many at the top of the WL won’t accept. They perhaps always preferred somewhere else that they got an offer from. Actually lots at the top of WL are in that position. Others might have preferred the WL school, but in the time since offers have come round to the idea of a school they had an offer from and decided a bird in the hand is worth two in the bush. People talk themselves into loving what’s available to them. If they’ve paid a deposit, this is even more the case. They have probably been to offer holders days, met some families who will be going there and are excited about the school they hold an offer for. So many on the WL who are given an offer say ‘no’. And the school finds it’s having to go down the WL. It’s having to wait for people to reply to offers and some take a couple of days and in that time things move on and more and more are sorted. So they have to go further down the list to those that they’re not quite so keen to take. If they reach a certain number of acceptances, they might decide to just stop there and not go down the WL further. They know that in the next 4 months, 2 or 3 families will contact them to say they’re moving into the area and they will be able to test them and maybe make one or two offers to strong candidates. So this is the more academic schools and bigger schools who can afford to do this. They aren’t quite so dependent on totally filing their 8 Forms and if they are 4 or 5 short, they’d rather have that than take weaker students. They know that in all likelihood one or two will appear part way through yr 7 or 8. They can be a bit flexible.
So, schools that have to use the WL or use it for more than a very small number if places, tend to be those that are less academic, probably smaller and it’s more urgent for them that they fill their places. Essnrtially they are much less selective. It’s why lots of schools have a WL, but never actually use it.
Sorry, not what people on this thread want to hear. And of course, people do get offers from WL every year. I think it’s v true that they often don’t release where people are on WL, because they want flexibility in who they offer to and will go for those they think will accept the place. It’s why staying in contact is important.