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<pre>In this work, we investigate the convergence and physical reliability of <br>truncated basis representations in solid-state high-harmonic generation by <br>comparing the stationary Bloch and accelerated Bloch bases. <br>We show that the two representations <br>exhibit intrinsic numerical inequivalence under strong-field driving, <br>leading to distinct carrier dynamics and harmonic emission.<br>The convergence behaviors of the two bases with respect to the number of <br>retained bands differ qualitatively, with the accelerated Bloch basis achieving reliable <br>spectral convergence using significantly fewer bands. By analyzing the deviation between truncated-band and full-band results, we <br>show that the energetically remote bands affect the harmonic generation through two <br>distinct mechanisms: the population leakage into higher bands, which mainly leads <br>to intensity renormalization, the modifications of the interband<br>polarization phase within the truncated <br>subspace, which cause structural distortions of the spectrum. These multiband <br>effects can be systematically incorporated into reduced two-band descriptions <br>through a band-folding correction.<br>Our results provide a physically transparent procedure for assessing <br>truncated-basis convergence and offer practical guidance for efficient <br>reduced-basis modeling of strong-field electron dynamics in crystalline solids.<br></pre>