Yes I have wondered that myself.
James Halfhead s of Joseph and Rebecca bap 29 Dec 1828 Haynes Beds
His father may have been;
Joseph Halfhead of Haynes Beds Committed 29 01 1822 aged 44 (born 1778) to Bedford New house of correction for 1 month hard labour offence stealing wood. Labourer 5 ft 5" Sandy hair, sallow complexion lost two front teeth, Orderly. Bedford Goal Record
Joseph and Rebecca had children bap Haynes 1821-1834.
There is a previous baptism for John Halfhead s of Joseph and Kezia bap 24 May 1819 Haynes Beds
There is also
Joseph Halfhead of Haynes Beds Committed 8 Apr 1811 aged 44 (born 1767) to Bedford Old House of correction for 3 months offence snaring. 5'5" Light Brown Hair, Swarthy complex, Orderly Bedford Goal Record
Joseph Halfhead married Jane Young 11 Aug 1790 at Haynes Beds and had children bap there 1792-1796 but the baptism I need for James Halfhead is around 1785 so before this marriage.
On the IGI there seems to be a gap in Halfhead baptisms between 1763-1790. I do not know if this is because the family were not in Haynes then or if there are missing transcriptions.