Frame numbers were there, but no arrow.
I haven't had the opportunity (or need/interest) to review the current version of the standard, ISO 732:2000,
Photography — 120-size and 220-size films — Dimensions, but in the past the "start mark" was formally known as "Register Mark for Automatic Camera" and specified as a specific distance from the start of the backing paper to the frame #1 marking, with accomodation for film clips used in development. It normative... a required mark with the form (arrow or whatever) being optional. Exposure number marking locations were standardized but here was no requirement for "warning markings" before the exposure numbers. In the last version of the standard that i've seen it wasn't even recommended, yet they are very helpful. The orientation of the exposure numbers was stated as a requirement and specified as an option of the manufacturer.
EDIT: The standard is silent on the use of arrows parallel with the backing paper which precede and align with the various frame number tracks. Hence, there is no specific requirement for them unless htat has been included in a later version of the standard than I have seen. But those arrows seem to be present often enough that they are generally provided for whatever benefit they may offer.
Regarding "warning marks" prior to exposure numbers... I can't recall what Portra used (despite shooting some in a folder camera just a few months ago) but they were present. For warning marks I recall that Ilford uses graduated dots; I think Portra uses the printed word "Kodak". I have memories of constantly missing "1" with old Tri-X because of the orientation of the number and my unfamiliarity with whatever warning marks they used.