Central Bank's own research shows 10% of mortgages are above the limit, namely between 3.51 and 4.5 LTI. As much as 17% are between the very narrow interval of 3.45 and 3.5! This 3.5 number is really, really binding in practice.
How binding the rules are shouldn't be a factor in the decision making process. While parts of the housing market are dysfunctional the part whereby estate agents extract the most they can from a purchaser works very well.
Change the rules and they will be binding very quickly