The title of the article in the OP and the OP itself are clickbait-ishly misleading. The issue isn't 5G, it's the proposed allocation of part of the 24GHz band that is adjacent to a critical frequency used for water vapor measurements without adequate limits on out-of-band emissions. I'll admit that it doesn't make for quite as snappy of a headline.
It's fine to have "concerns" but has anyone actually tested it?
Apparently, yes, both NOAA and NASA have conducted studies that concluded the proposed use of the spectrum would be detrimental to critical weather satellites. From the Ars Technica article:
The Navy memo cited NOAA and NASA studies on interference from 24GHz spectrum, which is intended for mobile use and is adjacent to spectrum used for weather operations.
"[A]s such, it is expected that interference will result in a partial-to-complete loss of remotely sensed water-vapor measurements," the Navy memo said. "It is also expected that impacts will be concentrated in urban areas of the United States first."
The memo suggested that the out-of-band emission limits should be reduced to at least -57dB.
The objections lodged by congress to the FCC's plans are based on the fact that the FCC has not provided a rationale for proceeding with their plan in spite of the objections lodged by the operators of weather satellites (and the consumers of the data furnished by those satellites, like the Navy). This is not unusual for the FCC under the current administration, which has plowed forward on a number of pro-industry initiatives at the expense of consumers and the public interest.