Syag, the reason he didn’t say it is a Halacha is because it isn’t. He didn’t say it is from Sifrei Kabbala because it isn’t. He said that women are Makpid because that is the case.
Al Titosh Toras Imecha does not contradict anything Chazal taught us. The Gemara actually says to take advice from the wife in domestic or worldly matters. The Gemara says that a woman has a better perception of her guests. This does not contradict the other statement, that Noshim Daatan Kalos, that it is easier to convince a woman.
If you think about it, it is a balance. The advantage of being more intuitive is balanced by the ability to be easily convined, and the advantage of mostly logical reasoning is balanced by being unaware of small telltale signs.
All of this, however, is besides the point. The idea is that we don’t mock something that is Nahug, just because one person over-reacted to you about it, or because you can’t figure out why it should be the case.
I think it’s a good Minhag, anyhow. First of all, for safety reasons, it is a good idea not to walk over a baby, especially while holding something — let alone a dangerous object. Secondly, it is a respectful gesture to walk around someone instead of over them.