Infinite window TBC

[DVtyro]

What does it mean? That is, what does it do and how does it work. Take this statement:

A time-base corrector, or TBC does one job: It corrects inconsistencies of an analog playback VCR. It accomplishes this by sampling one video scan line at a time (not an entire frame), corrects any instability by stripping the scan line of it’s old sync signal and replacing it with a brand new sync signal created by the TBC’s own built-in precise timing clock. Modern day TBCs, with their vast digital memory, can correct up to an entire field (262.5 scan lines) of incoming video. These are known as “infinite window” TBCs.

How come an field-size window becomes infinite window? Is there a qualitative jump from fewer than a field to a whole field? What exactly is infinite? Is it just a colorful figure of speech, or is there substance in it? I am going through Broadcast Engineering issues starting from 1972, but so far haven't found an explanation of the term.