you can say tens of something, i don't see an issue with that grammatically speaking.

"tens of thousands" literally derives from that phrasing even. similar to other weird anomalies like "ten hundred" which likely comes from "ten hundreds" for example

Technically speaking, any sort of arbitrarily defined grouping used in any numeral system can be used like this. For example 2^n would be relevant when discussing binary counting. You might refer to binary number groups as powers as a result.