"Among the many candidates were many men and women advanced in years".
They may have included people who weren't confirmed when adolescents because they hadn't been regular attenders at church at the time, or hadn't attended a C. of E. schools, or moved parishes in adolescence and missed confirmation visits by bishops.
The pre-confirmation baptisms may have been conditional baptisms if candidates didn't know if they were baptised as infants or couldn't provide proof. Were they born locally or had they moved to Hazel Grove? The vicar could have searched the baptism register if they were born in the parish, but if they were born elsewhere, he may have been faced with the prospect of writing dozens of letters to other parishes where people said they were born, to try to obtain proof of baptism. Considering the time it would take + cost of stamps, notepaper and ink, he may have decided that administering conditional baptism to them all was the best course of action. According to GENUKI, baptism registers for the church date from 1829, so if the oldest confirmation candidates were baptised as babies, their baptisms wouldn't have been in St. Thomas register. Boundaries of the parish changed c.1860 and changed again 1878 (source GENUKI).
A woman on a distant branch of my family tree was baptised "sub conditione" aged 34 although she's been baptised when she was a baby, like all her siblings. She and her 9 year old son were baptised on the same day at a Catholic church. Her infant baptism was at another R.C. church in the same town. Uncertainty about whether she was already baptised was probably caused by her stating the wrong year of birth and incorrect spelling of her surname by priests. Her surname has only 4 letters but there there are 3 variants of it in registers. Her infant baptism was written with a different variant to all her siblings. Her mother was R.C. but apparently her father wasn't. Her father was baptised "sub conditione" at a Catholic church , a month before his 78th birthday. His definitely comes under "late baptisms".