Halanto, jolly rumbello,
We were up long before the day-o
To welcome in the summer, the summer and the may-o,
For summer is a-coming in and winter's gone away-o

The tune is slightly modified to fit those words.
You'd have to ask Norma or Mike who modified the words and why.
They might have found an earlier version in some archives and it might have been that way until the 'folk process' took over. The Padstow May song has changed over the years, only slightly but enough to be noticeable.
But if Mike admits to writing the extra verse, then probably he 'adjusted' the rest of it.
However, we learnt the Waterson version first and it still feels easier to sing.

Robyn