Glyph origins of '進' Motivation

While writing my recent meta question, I've cited Dr. Gavin Chiu (趙善軒)'s article to explain the character '進' and its simplified character '井'.  However, a user points out that the linked article is not real academic material, and that such explanation is invalid.

Question

How do the glyphs '⻌' and '隹' come up together to bring the meaning of '進'?

My attempt

The bone script (甲骨文) for '進' reads .

In Shuowen Jiezi (說文解字), there's simply a one-line explanation.


  登也。从辵。閵省聲。


It's not hard to identify the left glyph in the ancient writing  in 說文解字 as '辵', but I can't understand the role of '登' in 說文解字's explanation for '進'.  The right glyph '隹' clearly represents a bird .

Source of images for ancient scripts: The Complete Collection of Ancient and Modern Characters (古今文字集成)
商甲京津4001合集32535隸定　
「進」 was originally constructed from semantic 「隹」 (picture of a bird) and semantic 「止」 (picture of a foot &gt; motion), indicating the flying motion of a bird, which infers the meaning forward, advance (birds cannot fly backwards). Later on, 「彳」 (left half of 「行」, picture of a road intersection &gt; roads, movement, path) was added to form the equivalent semantic component 「辵・⻍」 (walking, motion).
西周金圜器集成10360戰國・楚簡・帛帛乙8.5長沙子彈庫東漢隸白石神君碑　楷　

Note, 「辵」 is the full form of 「⻍」. As stated earlier, 「辵」 is made up from a merger between 「彳」 and 「止」, shown again via 「過」 below.
西周金過伯簋集成3907戰國・楚簡・帛語叢3 郭店楚簡秦簡效律9睡虎地秦簡東漢隸華山廟碑　楷　

References:

何琳儀《戰國古文字典：戰國文字聲系》
小學堂
國學大師

郭沫若《甲骨文合集》
中國社會科學院考古研究所《殷周金文集成》