If Pinny offers -111/+101 as a stopper, they get almost no bets at -111. They do get some at +101.
If they offered -112/+102, they would still get almost nothing at-112. The same chumps that lay -111 will lay -112 when -110 is everywhere... but Pinnacle's chump ratio is less than others. They would get almost the same volume on both sides at -112/+102 as at -111/+102.
The side they are offering +101/+102, they will get much more action.
Consider this position:
At an average price of -107/+103, Pinny takes 100k on fav -107, 50k on dog +103. They don't want a 50k naked position on a game where they have no opinion. The price crept up, and they put up the stopper: -111/+101 when most of the market is -110/-110. If the fav wins, they are down 50k. If the dog wins, they win 52k
surebets
2 hours to post: In the next hour, they take at 10k at -111 and 40k at +101. On this 1 hour of bets, their (1-hour) position is fav: win 30k; dog: lose 29.3k. The new net position (1 hour before post) is: Fav wins: -20k; dog: win 22.7k. In the last 10 minutes, they might take effective 0-juice positions to lower the volatility to as close to 0 as they choose...
The stopper doesn't prevent all bets at that price, but it drastically slows the flow of money on that side. And, they could usually lay off as much as they want at the market price of -110. Offering -112/+102 instead of -111/+101 means they pay a higher premium to reduce risk, with no real added benefit.