The issue can be seen with this code:
from textual.app import App
from textual.binding import Binding
class HelpLayoutApp(App[None]):
BINDINGS = [
Binding("f1", "gndn1", tooltip="This doesn't line up"),
Binding("f2", "gndn2", description="Does stuff", tooltip="This is fine"),
]
def on_mount(self) -> None:
self.action_show_help_panel()
if __name__ == "__main__":
HelpLayoutApp().run()
giving this:

note the extra space before the tooltip for f1.