Richard,
Isn't it a shame that the LDS do not allow the root sources of submissions to be given in the IGI?
Regarding your request about Henry John Swaffield's christening which, I surmise, was found as a submitted entry in the IGI. Think about the fact that the LDS submitter did not give HJS's parents' names yet the date is very specific. Why is that? If the christening record had been found in a church register against the given date, surely at least one parent's name would have been given? That makes me think that the entry may be a fairy tale or at least a part may be.
The LDS use various methods in arriving at unverified dates and places. From a church marriage record, guesses of the couple's "about" birth dates are arrived at (-21yrs for the bride and - 25yrs for the groom) Similarly, "about" marriage dates can be guessed from the age of the eldest child given in a census (- 1yr from birth year). Place of birth - same as marriage place might be given.
Extreme scepticism is needed when dealing with submitted IGI entries and you seem to be doing just that. The important thing to the LDS is that the person lived or is honestly thought to have lived. There is no intentional subterfuge on their part for dates and places are not very important to them and the IGI is for their use primarily.
But of course, the submitted entry might be the actual truth

Regards
Chas