That is an oft-repeated assertion that is in dire need of documentation. I decided to search this issue and despite over 50 results all i can find are answers such as this:
I heard that Vote by Mail ballots are only counted if a contest is close. Is that true?
No;
All valid Vote by Mail ballots are counted. Because voters are
cautioned that Vote by Mail ballots returned to the polls on Election
Day will not be included in election night results, this has been
misunderstood to mean they are not counted at all. This rumor is likely
due to a misunderstanding of how Vote by Mail ballots must be processed.
Because signatures on Vote by Mail ballots must be verified before the
ballots can be counted, ballots received within 1-2 days prior to
Election Day may not be counted and included in semi-final results
reported election night. It may take up to one week to verify all
signatures on Vote by Mail ballots returned close to, or on, Election
Day before the votes cast can be counted and included in the final,
official results.
(http://vote.sonoma-county.org/...
I’ve heard that absentee ballots are only counted if they will affect the outcome of the election. Is this true?
No. All absentee ballots that are received on time are considered for
counting. Absentee ballots received by Election Day are counted on
Election Day. Ballots received after Election Day but before the
deadline are counted when the absentee and special voters’ precinct
board meets as long as they are postmarked the day before Election Day
or earlier. (https://sos.iowa.gov/elections...
Are special ballot counted even if they will not change the outcome of the election?
All qualified votes cast by special ballot are tabulated. (https://www.dcboee.org/faq/vot...
Myth: Absentee ballots only count in close elections.
Reality: False. Absentee ballots submitted in accordance with state laws are counted for every election. The difference is that in a close election the media reports that the outcome cannot be announced until after the absentee ballots are counted. However, all ballots are counted in the final totals for every election -- and every vote (absentee or in-person) counts the same. - https://www.army.mil/article/134530
Ballots received after Election Day but before the
deadline are counted when the absentee and special voters’ precinct
board meets as long as they are postmarked the day before Election Day
********************
It was on this basis that Gore tried to get military absentee ballots thrown out in Florida 2000.
It didn’t work as many other rotten democrat schemes that year didn’t. Amplifying the importance of having a conservative Supreme Court.