A new preprint on arXiv (v1, 15 May 2026) revises GJ 3378b using joint radial-velocity modeling from HPF on the Hobby-Eberly Telescope, NEID on WIYN, plus published CARMENES and SPIRou data. The analysis lowers the minimum mass from 5.26 to 2.3 Earth masses and shortens the period from 24.73 to 21.45 days while keeping the orbit inside the conservative habitable zone of the nearby M4V star. This preprint is not yet peer-reviewed. The smaller mass raises the odds of a rocky composition, yet simultaneously places the planet exactly on the cosmic shoreline—the empirical threshold where stellar XUV-driven escape strips atmospheres from planets around active M dwarfs. Earlier coverage of the Moutou et al. 2024 SPIRou-only detection missed how modest changes in period and mass shift a world from potentially thick-atmosphere to marginal-retention regime. Cross-referencing with Zahnle & Catling (2017) shoreline relations and the Owen & Wu (2017) energy-limited escape framework shows that GJ 3378b now sits near the boundary where even modest stellar flare histories could remove several Earth-ocean equivalents of volatiles over gigayears. The RV-only method yields only m sin i, leaving inclination and true mass unknown; stellar-activity jitter and limited phase coverage remain key limitations. Future transmission spectroscopy with JWST or ANDES could test whether a thin atmosphere persists precisely because the planet straddles this divide.