I agree with it. If you want to go with multiple XML site maps so you have to wait after submission.

I have very good experience with multiple XML site maps.

I am working on eCommerce website and submitted 24 XML site maps to Google webmaster tools.

Just look in to multiple XML site maps for Lamps Lighting and More!

You can see that Google webmaster tools shows very few index URLs.

I have similar experience for my another eCommerce website where I have submitted 7K+ URLs and 300+ indexed by Google with in 15 days.

I read some where as follow. So, which is right? I am too confuse...

a single feed can handle up to about 100,000 items of
all types and categories -- from handbags to hammers.

up to 10 feeds may be registered for up to 1,000,000 items.

multiple feeds are mainly intended to submit
more than 100,000 items -- not as a general
separation of products.

there are various issues associated with multiple feeds
that should be taken into account -- such as coordinating
unique id values across all feeds and update and upload
coordination issues; but 10 registered feeds are allowed.

I have submitted my product feed to Google Merchant Center. There are 7K+ products in one product feed. (data_feed.txt)

I am not satisfy with my products' performance on Google shopping. Because, I am not able to maintain data quality for all products as well as not able to focus on high selling categories.

Can I submit multiple product feed with separation of categories as follow.

category001_data_feed.txt (With 200 High selling products)

category002_data_feed.txt (With 100 offers products)