Sven,
You are correct, Abington Hills was built from late 1923 on into early 1925. I have a number of articles which I'll post later on that detail the work during 1924. The reason for the early incorrect date has to do with when the dates for the creation of the Tilly courses were first gathered and from where.
Today we really take for granted the super-abundance of information that a determined researcher can find via the internet; yet even still mistakes are made.
Originally Abington Hills and The Abington Club were mixed up because the Abington Club contained the following on its website: "The Abington Club originated as Old York Road C.C. in 1909. A small group of men from the Jenkintown area secured an option on 67 acres from the Abington Friends meeting. By 1910, the required 100 original members had been secured. A contest to design a 9 hole golf course was held and won by Mr. Lang, the golf professional from Huntingdon Valley C.C. In 1912, an additional 35 acres was leased. The 18 hole golf course opened for play in 1913... During the period of 1915-1917, changes and improvements to the course were made by A.W. Tillinghast."
Now Old York Road (which Tilly did redesign and add onto in the late teens) did give rise to the Abington Club when and that occurred in 1962 when Abington Friends Meeting, from whom they leased the land for course and club, asked them to leave as they now needed their land to expand their school.
It was because of the mistake in the name "Abington" and how it was used in connection to Old York Road which Tilly did that the mistake in date and club was made, this also being exacerbated by Abington Hills CC as being NLE.
As I said earlier, I'll post several articles for you later... Nice find.