Wikipedia claims the weighting for baseball started in 2013 and is as described here for true home v. true road environments.
'The formula used in NCAA baseball is the same as that used in basketball except for the adjustment of home and road records. Starting in 2013, college baseball RPI formula values each road victory as 1.3 instead of 1.0. Each home win is valued at 0.7 instead of 1.0. Conversely, each home loss counts 1.3 against a team's RPI and each road loss counts 0.7 against a team's RPI. Neutral-site games have a value of 1.0, but the committee is studying how to determine if a game should be considered a neutral-site contest. The adjustment is based on data showing that home teams win about 62 percent of the time in Division I baseball."[6] The change was made because of the discrepancy in the number of home games teams play. Some schools are able to play 3540 of their 56 allowable games at home, while other teams, due to factors such as weather, may play only 20 home games.
This adjustment replaces the previous system of bonuses or penalties that teams received. Bonus points were awarded for beating top-75 non-conference opponents on the road and penalty points were given for losing to bottom-75 non-conference opponents at home. Bonuses and penalties were on a sliding scale, separated into groups of 25, with the top bonus for a road win against a top-25 team and the worst penalty for a home loss to a bottom-25 opponent.[6]'
https://en.m.wikipedia.org/wiki/Rating_percentage_index (See baseball formula section)
