Your example is valid in ISO 8601-1:2019.

There are only two possible representations for which "T" is required: hh or hhmm in 'basic' format (i.e. no ":" separator). The former could be confused with a two-digit century, the latter could be confused with a four-digit year. Adding "T" to hh or hhmm solves this.

Any of the following eliminates the "risk of confusion":

  - 'extended' format (hh:mm)
  - decimal fraction (hhmm,m or hh,h; see 5.3.1.4);
  - UTC designator (hhmmZ or hhZ; see 5.3.3), or;
  - time shift (hhmm±hhmm, hhmm±hh, hh±hhmm, or hh±hh; see 5.3.4).

Also worth noting: hhmmss in 'basic' format (i.e. no ":" separator) does not pose a risk of confusion, as YYYYMM in 'basic' format (i.e. no "-" separator) is not permitted by the spec.