The landing page templates use a simpler header than the other pages. It contains only the logo, without the Website header module, so the logo size is not set in the header module.
Open a landing page in the page editor, click Global theme styles and go to Other settings > Landing page header. Switch Override logo width on, enter the width in Logo width and click Publish changes. This applies to every page built on the landing page templates. The value works as a maximum width: it shrinks the logo but does not enlarge it beyond the size of the uploaded image.