This has thankfully been fixed in 4.3.4
With the sitemap in 4.3.3 and 4.3.4 now fixed, my indexing has gone up from 17849 pages to 22,229 (pretty much over the last 4 weeks) with just about the same submitted, less the new content. I do believe adding the timestamp helped and I'm still waiting for all my images to be indexed because before the latest ips sitemap change, google was not picking up the extra image sitemap or video sitemap. Now there is clearly a content section for images and video as separate sitemaps within the sitemap. I do think there is an opportunity for those that want to use it, to include additional topic and other secondary content pages in the sitemap as well as a news sitemap for those that use the pages app.