Ancestry hints are notoriously wrong most times. Best not to base your FH from them.
Most trees, and there are many (not all correct) for both William & Ruby have his birth as
WILLIAMS, WILLIAM THOMAS mmn JENKINS
GRO Reference: 1900 J Quarter in BRIDGEND Volume 11A Page 839
Which would make sense as they married in Bridgend reg district. As mentioned the marriage cert is a must in Welsh research.
There is a possible in the Llangeinor area 1901/1911 with parents John & Hannah. Hopefully the marriage will confirm father. As well as address.
https://www.genuki.org.uk/big/wal/GLA/Llangeinor Good luck
Cas