I know plenty of quality female engineers who would be greatly offended or disturbed, not to mention female employees overall - it isn't about the he/she controversy itself necessarily (although using male gendered pronouns exclusively has a long history of intimidating women & making them feel less welcome). It may also offend quality male engineers, who feel like the culture at the company is not as rosy as they expected. As a male engineer myself, if I saw such signs, I'd think about jumping ship simply because leadership isn't thinking at a high level about the effects of their actions (or inactions), and word has a habit of getting around (and in this case, it is visible enough as is). Just as companies don't want to associate with something less desirable most of the time, there is a lot of quality employees that feel that way about employers.

Tech companies like to bill themselves as great places to work for all prospective employees they court - this is the type of issue that is exactly an instant dealbreaker for many out there if it is not handled decisively.