To reproduce:
1. Open any project;
2. Navigate to Particles/Lit or Particles/Unlit shaders in URP package;
3. In the Inspector, under Compiled code dropdown, select GLES20 and GLES3x;
4. Press Compile and show code.

Expected result: no warnings are thrown after shader compilation.
Actual result: up to 342 warnings are thrown: "conversion from larger type to smaller, possible loss of data"

Tested and reproduced with URP versions (master branch):
d4d9c2c57dc671a9406470f32b3fe12668d8346e
41a9e99530ec7e37f7b29e35bd0d7ccce4858294
d4c53d60e84b4ecd487730da7a8e61d1593bd339
d0aede8a49d36e76de3679725b53d4ba05a452db
53114f4b5cdb0f92e120dfb69f5ba3652fd7f47b
2423f14de7d51a75811cd00b0bb63aff77822207

Not reproduced with: 10.3.1